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What we did in Chemistry B today      posted 08-09-2010
Today is 9 August 2010. Today in class we finished making slide rules and started using them to learn scientific notation and significant figures. We applied the methods and used the slide rules to solve a problem involving gas laws. You also had three questions to answer and hand in on your way out the door.

Remember, the slide rule will never replace the electronic calculator or computer, but until you, my students, have enough practice to understand numbers used in scientific work, it is a great teaching aid. I asked you to practice multiplying and dividing with it as homework. Please compare your answers to those you get by working longhand. Here is a sample problem: What is Avogadro's number? Look in your lab book, if you do not remember offhand. What is the volume of one mole of an ideal gas at standard temperature and pressure (STP)? That is in your notes, too. What is the volume (ml, L, any volume unit you choose) of one molecule (or atom, in the case of noble gases) of ideal gas at STP? Remember to use scientific notation, methods of estimation, and then convert your answer back to standard format. Please have your work written in your lab book and present it to me tomorrow in class.

(This blog is also being sent to you as email.)

JLStern

What we did in Chem B today      posted 07-30-2010
We started the Gas Laws. We described Gay-Lussac, Boyle and Charles' Laws. We worked sample problems and discussed the history of how the laws were developed. I said that math applied to science continues to be a challenge for many students, and that when you understood the basics, your minds would be free to study other matters -- that would help you become better students. To help you in this, I offered to teach you how to make and use the slide rule to multiply and divide, and other math functions used in science. This would be (basically) on line with some time after class. Bonus credit would be given to those who are interested. About 6 students from period one showed interest. We'll try period 2 tomorrow.

Homework: Select AT LEAST three problems from EACH of the problem groups on page 446 of your text starting with problem 35 and going to problem 51. It would be best if you do all 17 problems, but 9 is acceptable. REMEMBER: that is 3 from Nos. 35 - 40; 3 from 41 - 46 and 3 from 47- 51.

On Monday, 2 August, be sure to bring your water bottle with the steel wool inside ("in Rust We Trust" experiment). We will check the final volume and weights. You will then have until Wednesday to hand in the report of the experiment.
JLStern

Acid/base equilibria test      posted 07-26-2010
As promised, here is the exam. You took notes on how the reaction proceeded. Now, study the model problem and answer the questions. (DUE TOMORROW, 27 JULY 2010 -- AND THE LAB (COMPLETE) IF NOT ALREADY TURNED IN.)


INSTRUCTIONS: Read this exam carefully! A practice problem is worked out for you. Understand it and then apply to your ACTUAL lab data. Show ALL work. You will have 60 minutes. The exam is worth 100 points. DO NOT WRITE ON THIS TEST SHEET. USE THE PAPER SUPPLIED.

A. Reactions of Magnesium

2Mg + O2 ⇒ 2MgO
MgO + H2O ⇒ Mg(OH)2
Ksp = 1.5 x 10 -11
Mg(OH)2 + H2SO4 ⇒ MgSO4 + 2H2O
Mg(OH)2 + 2HCl ⇒ MgCl2 + 2H2O

1. Assume 0.010 g Mg. How many moles of Mg is that?
(moles = mass/At. Wt. = 0.010 g/24 amu = 4.16 x 10-4)
2. Mole ratio of Mg to MgO is 1:1. Therefore, 4.16 x 10-4mole of MgO is formed.
3. Formula weight of MgO = 40. Mass of MgO = (4.16 x 10-4)(40) = 0.0167 g.
4. Assume recovery of 0.008 g or 48%. (0.008 g/0.0167 = 0.48 = 48%)
5. When added to water, solution pH is 8.5. pH = - log [H+] so,
8.5 = - log [H+]
- 8.5 = log [H+]
antilog -8.5 = antilog (log [H+])
10-8.5 = [H+] = 10-9 x 10.5 = 3.16 x 10-9
Since Kw = [H+][OH-] = 1.0 x 10 -14
[OH-] = 1.0 x 10-14 / 3.16 x 10-9 = 0.316 x 10 (-14 – (-9)) = 3.16 x 10-1 x 10-5
[OH-] = 3.16 x 10-6 M = 3.16 x 10-6 moles per liter
6. Since formula is Mg(OH)2, and 3.16 x 10-6 moles per liter is the TOTAL [OH-] per liter, the concentration of Mg(OH)2 must be 3.16 x 10-6 moles/2 = 1.58 x 10-6 moles per liter. The mass of Mg(OH)2 is (1.58 x 10-6 )(24 + (2)(17)) = 9.16 x 10-5 g.
7. Acid (H2SO4 or HCl) was added. The concentration is 1 M (1 Molar or 1 mole per liter). It reacted with the dissolved Mg(OH)2 to form MgSO4 and water (or MgCl2 and water). As it reacted, more of the MgO was able to react with the water to form more Mg(OH)2 which then reacted with the acid, and so on util the MgO was all used up.
8. If the only Mg(OH)2 was the amount that originally dissolved, and it was in 50 ml water, not 1 liter, the amount of Mg(OH)2 that would have reacted would have been (50 ml / 1,000 ml per liter) (9.16 x 10-5 g) = 4.58 x 10-6 g.
9. However, since 0.008 g MgO was recovered and eventually reacted, the amount of MgSO4 possible for recovery is in a 1.0 : 1.0 ratio. (What would it be for MgCl2?) Thus, [(0.008g/(24+16) amu MgO per mole] x (24 + 32 + 64) amu MgSO4 = 0.024 g.
10. But you don’t know how much water there was. It was not measured. You do know the final weight. If the beaker weighed 45.57 grams, then the gross weight of MgSO4 with beaker would be 45.59 g.
11. You know how much Mg you started with. From your lab report, how much was that? _____________ You know how much MgO you recovered. From your lab report, how much was that? _____________ You know what the final weight was of either the MgCl2 or MgSO4 that you recovered at the end of the experiment. From your lab report, how much was that? _____________ You also know how many drops of acid you added. From your lab report, how much was that? _____________ How many ml of acid is that, based on your finding of the number of drops to make a ml? _____________ Now, calculate the following:
a. Moles Mg at start.
b. Weight of MgO theoretically possible.
c. Percentage of MgO actually recovered.
d. Weight of MgSO4 or MgCl2 theoretically possible.
e. Percentage of MgSO4 or MgCl2 actually recovered.
f. Moles of acid needed to react with the Mg(OH)2.
g. Moles of acid you actually used.
h. When you heated the MgO, some students reported that the pH increased to 9. What is the [OH-] concentration when the pH is 9?
B. Write and balance the following reactions using the algebraic method:
1. K4Fe(CN)6 + H2SO4 + H2O = K2SO4 + FeSO4 + (NH4)2SO4 + CO
2. KMnO4 + HCl = KCl + MnCl2 + H2O + Cl2






About Acid/base equilibrium test      posted 07-25-2010
Students:

The test scores were very low. It is obvious that you need more practice in balancing chemical reactions. I will provide more opportunity to practice. The questions that required you to provide input from your lab is another story. If you won't do the work and won't write down the data from your experiments, you will have a problem. As I reviewed the lab reports, I saw that most students did not bother writing up a report of the experiment or even write down the results from weighing the samples at various stages. How much effort, really, is involved in weighing an empty beaker, weighing it after burning a strip of magnesium and weighing it after you reacted an acid with the MgO, and evaporated the liquid? You were instructed to count drops to get to an end point; you were taught how to convert the number of drops to milliliters, and you were shown that the molarity of the acid was 1 M. All of this you were taught. At every step of the way, I asked for questions. At every step you were given a chance to demonstrate understanding. What happened between the instruction and the exam?

High school is supposed to be rigorous. (If you don't know the meaning of "rigorous," look it up in a dictionary.) Your teachers are not supposed to give you crayons and paper and limit your education to making pretty pictures. Chemistry class requires you to study material presented and to complete assignments. You need 60% of the available points to pass the class. Right now, most of you are not passing. If you look at your personal report card, you will see that the majority of those who are not passing have not turned in assignments. Remember, 30% of the grade is based on lab reports, 30% on tests, 30% on classwork and 10% on homework. A student can fail all of the exams and STILL pass the class if they do the other assignments. What, really, is the big problem?

--Jay L. Stern

Equilibrium & Acid/Base Reactions      posted 07-22-2010
Following from our study of equilibrium constant and solubility product, we are conducting an experiment involving (1) burning magnesium, (2) collecting the magnesium oxide that results, (3) mixing it with water to form magnesium hydroxide, (4) adding acid to convert the magnesium hydroxide to a magnesium salt, (5) evaporating the liquid and (6) weighing the residue to determine what is in the salt. Through it all, weighing and the mole concept are important concepts to be mastered. The questions to be considered and the points involved in metacognitive analysis of the experiment are:


Acid/Base Equilibiria

1. What is an acid?
2. What is a base?
3. You react Mg with O2 in the air. What kind of reaction is that?
4. What is the product of the reaction? Write it out and balance the reaction equation.
5. You want to collect and quantify the product of the reaction. How is this done?
6. After you collect the reaction product, you try to dissolve it in water. The solubility product is Ksp = 1.5 x 10-11. What does this tell you about the solubility of the product of the reaction?
7. You test the solution with a piece of pH paper. The color indicates a pH between 8 and 9. What is the best accuracy you can say for the pH?
8. If you heat the solution, you think you have more reaction product dissolve. What is a way to determine this? What chemical principle would allow this way to work?
9. To convert the reaction product into a sulfate or chloride salt, you can add drops of sulfuric or hydrochloric acid. What is the formula for each of those acids?
10. Write the reaction between the reaction product (in water) with the acid, and balance the chemical equation for the reaction.
11. The acid solutions you have are 1 M. What does this mean?
12. What is your evidence that a reaction between the acid and the reaction product has occurred?
13. You need to convert the number of drops of acid you added to your reaction product solution into milliliters. How is this done?
14. You want to calculate the “yield” of the oxidation of the Mg. What did you do?
15. You want to verify your work by calculating the amount of acid that reacted with the reaction product. How did you do this?
16. You can evaporate the liquid from the salt that formed when the acid reacted with the reaction product and weigh the residue. How do you do this? What measurements do you need to make? What equipment do you need?
17. What are the names, common or scientific, for the salt that results?
18. What chemistry principles have you learned from this experiment? (Think of acids and bases, equilibrium, balancing equations, etc.)

DO A GREAT JOB ON YOUR LAB REPORT!!!

Equilibrium test "Equilibrium essay"      posted 07-18-2010
Here is a model essay:
"Explain how equilibrium is involved in oxygenating animal tissue."

First, find three things relating equilibrium and oxygenation of tissue.
1. Forward rate equals reverse rate
2. Animal tissues need oxygen
3. Animal tissues need carbon dioxide removed

Second, write a sentence for each of the "things." Then, enlarge the sentence to a paragraph.

1. Chemical equilibrium is when the forward rate of a chemical reaction equals the reverse rate. The reactions occur at the same time. One reaction goes one direction; the other reaction goes the other direction. The reactions are the opposite of each other. The rates are in balance with each other.

2. Animal tissues need oxygen. They get the oxygen from the blood which transports it. The blood picks up the oxygen in the lungs of land animals, and from the gills of aquatic animals. Iron in the blood is what binds to the oxygen. It holds the oxygen until the blood moves to a place in the body where the concentration of oxygen is low. Then the oxygen is released to the tissue.

3. Carbon dioxide is produced as the oxygen combines with carbon produced from foods. This carbon dioxide needs to be removed from the body. It does so by exchanging with the oxygen. As the oxygen is released from the red blood cells, the carbon dioxide binds. This causes the concentration of carbon dioxide to be greater than the concentration in the air. When the blood circulates to the lungs, it is released because the oxygen from the air displaces it.

Then, I would put an introduction on the essay, and write a conclusion which highlights what I have written in the body of the essay. This IS NOT A DIFFICULT THING TO DO!!

You would have written similar essays for the other topics I gave you:
-- Describe how equilibrium is used to produce products (examples; Haber process, production of various salts).
-- Why are significant figures and scientific notation useful in scientific work

NOTE: ALL OF THESE TOPICS WERE THOROUGHLY COVERED IN CLASS!!!!!




Equilibrium test "definitions"      posted 07-18-2010
Possible answers for the Equilibrium test are as follows:

Definitions:
1. Saturated solution: A solution which is so concentrated that added solute will not dissolve.
2. Dynamic equilibrium: A chemical reaction in which the reverse reaction occurs at the same rate as does the forward reaction, thereby maintaining equilibrium.
3. Strong acid/weak acid: Strong acids disassociate completely in solution; weak acids partially disassociate.
4. Azeotrope: A mixture of two (or more) substances that cannot be separated by distillation because they form a mixture with a constant boiling point.
5. pH: Literally, the "power of Hydrogen." It relates to the number of hydrogen ions in solution. The acid/base level. You can also give the equation pH = - log [H+].




Equilibrium test results      posted 07-18-2010
My records show that only one student who had been absent on the day of the Equlibrium test made it up. It is too late now. Anyone who did not make up the test by Friday, 16 July, has a zero.

The results of the exam were awful. The high score was a student in period 1 who got 94 out 100. The low score -- and there were MANY-- was zero. The mean for period 1 was 36; for period 2 it was 22.

Several things were obvious from the test: (1) Many of you are not bothering to study at all. You come, sit in class, and that seems to be the extent of your "learning." That is not acceptable. (2) Some of you appear not to know how to write a student essay, even when coached. You were directed to write a 5-paragraph essay on each of TWO topics and to define five terms. That means TWO essays. Many of you wrote a few sentences or paragraphs that combined the two topics, or just attempted to define one or two of the terms. (3) Related to (2), most of you will not follow instructions. This has to change if you expect to succeed in this class, let alone pass it!

The Equilibrium test focused on writing, since so many of you have major difficulties with math. But the really bad results show that you have trouble with writing, too. It is up to you to improve. I will not "dumb-down" the course to accommodate students who choose not to put out enough effort to pass.

The tests will be returned on 19 July. They will be attached to a note for your parents. You are required are to take the note to your parents. I want your parents to call me to discuss ways to help you learn better. If I do not receive a call back by 22 July, I will conclude that YOU have not taken the note to your parents, and I will take further action, including suspension or expulsion.


Lesson plan for Chem B, 12 - 14 July 2010      posted 07-12-2010
Lesson Plan: Chemical Equilibria

A. Reversible Reactions and Equilbrium
1. Key terms:
a. reversible reaction: reaction which is reversible due to concentration, temperature or pressure changes
b. completion reaction: reaction which reactants produce products and will not reverse under ordinary conditions
c. chemical equilibrium: condition at which rate of conversion of products to reactants equals rate of conversion of reactants to products. Referred to as dynamic equilibrium
d. complex ion/coordination compound: metal ions/atoms which reversibly bind to other atoms or molecules. Best example is reversible binding of oxygen to iron in hemoglobin.

2. Example reactions:
a. irreversible -- CH¬4 + O2 → CO2 + H2O
b. reversible – CaCl2 + Na2SO4 ⇔ CaSO4 + 2 NaCl,
2 NO2 ⇔ N2O4
(Demonstation: Add copper to HNO3 to make NO2 + H2O + CuNO3 The NO2 will be a red gas. It is dense and can be poured into tt which are then stoppered. Put tt in boiling water; it turns brown; put in ice bath, it decolorizes. Link to formation of SMOG.)
i. History: The concept of a reversible reaction was introduced by Berthollet in 1803, after he had observed the formation of sodium carbonate crystals at the edge of a salt lake: 2NaCl + CaCO3 → Na2CO3 + CaCl2. He recognized this as the reverse of the familiar reaction Na2CO3 + CaCl2→ 2NaCl + CaCO3

3. Assessment:
a. In reversible reactions, does it matter if you start with reactant or product? Explain.
b. What types of conditions drive reversible reactions?
c. Carbon monoxide binds irreversibly to hemoglobin. What sort of reaction is this? What are the consequences of this?

B. Systems at Equilibrium
1. Key terms:
a. equilibrium constant, Keq
b. solubility product constant, Ksp
c. stalactite
d. stalagmite
(look at figure 6, p. 502. What color are stalactites? What color are stalagmites? Do you agree that they are “beautiful?” Why? Do you think color determines beauty? What color is calcium carbonate, as in chalk? Is your book misleading you since the picture shows color, but calcium carbonate is white? How do you think the color in the picture was produced?

2. Why is equilibrum constant important?
( Because it is used to determine the rate of reactions at equilibrium.)
3. How is the constant determined?
(From the concentration of the reactants and products)
4. From the text, what are the steps?
a. Write and balance the chemical reaction
b. Write the equilibrium expression: product in numerator, reactant in denominator:

Keq = [P1]x[P2]y / [R1]a[R2]b

c. Use brackets to denote “concentration.”
d. Leave out of expression solids or liquids that do not change
e. write term coefficients as superscripts.
5. Textbook example:

H2CO3(aq) + H2O (l) ⇔ HCO3- (aq)+ H3O+ (aq)

Concentrations: carbonic acid – 3.3E-2 mol/liter
Bicarbonate ion – 1.19E-4 mol/liter
Hydronium ion – 1.19E-4 mol/liter

6. Assessment: Do practice problems on p. 504

7. Understanding:
Look at table 3, p. 505. Notice the results of the various reactions. What does it mean when the Keq is large? What about when it is small? Inspect the equations. How would you increase/decrease the various equilibrium constants? (READ AND KNOW FIRST AND SECOND PARAGRAPHS ON P. 505.)

Observe (p. 506) that one can work “backwards” from the Keq and reactant concentrations. Work out the sample problem and the two practice problems on p. 506.

8. Compare Ksp to Keq. What is the difference? What is the similarity? Why do we need to understand Ksp?



A. Equilibrium Systems and Stess: LeChatlier’s Principle



Chem Class, 7 - 9 July 2010      posted 07-09-2010
I offered a refresher of what you were already supposed to have learned in Chemistry A, or prior science classes. I am concerned that so many students seem not to understand the mole concept, scientific notation and significant figures. Further, most of you need to drill on basic math operations including long division and exponents. You had a homework problem: The diameter of the earth is 8,000 miles. The equation for the surface area of a sphere (e.g. -- our planet) is S = 4 Pi r^2 (where "r^2" means radius squared). We solved that. You were told that the length we call a "meter" was originally set at 1/10,000,000 the distance from the north pole to the equator. You were reminded that area of a circle is A = Pi r^2 and asked to find the surface area in square meters.

We discussed the number of particles in a mole: it is 6.02E23 (where "E23" is a short-hand way of writing "10 to the 23rd power.") We spoke of ways to memorize the number and how to use it. Basics of math were covered, like how to divide two numbers (the denominator goes into the numerator; not the other way around).

We started to discuss equilibrium, one of the topics we are to cover in Chem B. You were to read and summarize Ch. 14, section 3 in your text. Instructions were given on how to "preread" a text. Homework for the weekend was to preread sections 1 and 2. I attempted to demonstrate equilibrium with salt solutions and acids, and it didn't work very well. I need purer chemicals to show you. We'll try again Monday.

For the lesson plan for 12 - 13 or 14 July 2010, see the next blog.

Enthalpy measurements -- Handwarmer lab      posted 05-09-2010
Hi !NAME!,

I'm afraid the lay-flat plastic tubing that I provided you has degraded over time. I've had it for several years. This is probably why those of you who tried to seal water in the bags made from the tubing had leaks. Until I can get some better plastic, we will have to finish the experiment another way. I still want you to learn about heat capacity so here is what we can do:
1. Accurately weigh out some dry sodium acetate crystals. Use at least a gram or two in a small beaker.
2. Put the beaker in a hot water bath until the crystals melt.
3. Take the beaker out of the bath and immediately put a thermometer into the melt. Hold the thermometer so it doesn't fall out and shatter. Record the initial temperature and the time. Keep the thermometer in the melt until the crystals resolidify. Record the temperature at time intervals. You might try two minute intervals.
4. Prepare another beaker, larger than the one holding the crystals. Accurately weigh twice the weight of water as crystals and put it in the larger beaker.
5. Clean off crystals that may be sticking to the thermometer. Add those crystals back to the smaller beaker.
6. Put the thermometer in the larger beaker. (Mount it so it doesn't fall out.) Take the initial temperature of the water.
7. Return the beaker with the crystals to the hot water bath. As soon as the crystals melt, put it in the beaker with the water. Swirl the beaker to warm the water as quickly as possible.
8. Keep watching the thermometer. Record the temperature as it rises to a peak (and the time), then starts back down. Keep measuring time and temperature. When the sodium acetate in the smaller beaker starts to re crystallize, note it (time and temperature). You might see an increase in temperature at that point. That would be due to the heat of crystallization. If it does increase, great! Track it. It will hit a maximum, then start cooling. The difference between the maximum temperature and temperature when the crystals started to form is due to the heat released from crystallization.
9. You know the heat capacity of water: 1 calorie per gram per degree C. With this, the moles of water and the temperature difference, you can calculate the heat released by the sodium acetate. That heat is the same needed by the sodium acetate to melt. If you get two temperature peaks, you can calculate the heat released during crystallization.

10. Here is the equation again; q = Cp x moles x (T1 - T2)


Solutions Chemistry Quiz      posted 03-28-2010
Student results for the "Solution Chemistry" test conducted 26 March 2010 were not good. It was obvious that most students did not study nor attempt homework which would have assisted them in successfully completing the test. I am going to show you how to set up each problem. You still have to solve the problems! You will have the opportunity to retake the test on Monday, 5 April 2010, after school. If you do not open your email to read this message, I can't do anything about that. If you take this opportunity, I will average the two grades for a final score.

Mr. Stern

NOTE: "(aq)" means aqueous (e.g. -- "in water")
NOTE: I can't print subscripts in this Blog. You need to know, for example, that "C2H5OH" means 2 atoms of carbon, 5 of hydrogen, one oxygen and one more hydrogen.

i. "Define Molarity"

Check the text definition.

ii. Define "Molality"

Check the text definition.

iii. Define "parts per million."

Check the text definition.

1. A 0.750 L aqueous solution contains 90.0 g of ethanol, C2H5OH. Calculate the molar concentration of the solution in mol·L-1.

Want molarity (M) = moles/liter. Moles = grams/atomic wt. So M = moles/0.75 liter

2. What mass of NaCl is dissolved in 152 mL of a solution if the concentration of the solution is 0.364 M?

Want mass NaCl. M = moles/liter = 0.364 molar = moles/0.152 Liter. Solve for moles.
Then, since moles = mass/At. Wt. Rearrange for (At. Wt.)(moles) = mass

3. What mass of dextrose, C6H12O6 is dissolved in 325 mL of 0.258 M solution?

Want mass C6H12O6. M = moles/liter 0.248 M = moles/0.325 liter
mass = moles x at. wt.

4. A mass of 98 g of sulfuric acid, H2SO4, is dissolved in water to prepare a 0.500 M solution. What is the volume of the solution?

Want Volume. Find moles; moles = mass H2SO4/At. Wt. Then Volume = moles/0.5 M

5. A solution of sodium carbonate, Na2CO3, contains 53.0 g of solute in 215 mL of solution. What is its molarity?

Want molarity. Find moles; moles = 53 g Na2CO3/At. Wt Na2CO3.
Then M = moles/0.215 Liter

6. What is the molarity of a solution of HNO3 that contains 12.6 g of solute in 5.00 L of solution?

Want molarity. Find moles; moles = 12.6 g HNO3/At. Wt. HNO3. Then M = moles/5.0 liter.

7. What mass of copper(II) nitrate, Cu(NO3)2, is present in 50.00 mL of a 4.55 x 10-3 M aqueous solution?

Want mass. M = moles/liter; 4.55 x 10-3 M = moles/0.050 liter. Then mass = moles x at. wt. of Cu(NO3)2

8. What volume of 0.778 M Na2CO3 (aq) solution should be diluted to 150.0 ml with water to reuduce its concentration to 0.0234 M Na2CO3 (aq)?

Want volume. First find moles: M = moles/Liter. Rearrange for (0.778 M Na2CO3) x 1 liter = moles. Then divide by 1000 ml/liter for moles per milliliter. Then calculate how many moles needed for dilute solution; M = moles/liter = 0.0234 M Na2CO3 = moles/0.150 liter. Since M means "moles per liter," the liter unit cancels out when you do the math. You have moles needed which you divide by the answer to the first part. That is in moles per milliliter. Moles unit cancels and you have answer in milliliters.

9. A 25 ml sample of HCl (aq) is diluted to a volume of 500 ml. If the concentration of the diluted solution is 0.085 M, what was the concentration of the original solution?

Want Molarity. Dil HCl = 0.085 M = moles HCl/liter. Rearrange to find moles HCl. Then find how many moles in 0.5 liter: 0.5 liter x moles/liter = moles available.
Original concentration = M = moles available/orig. vol. = concentration, M




Hollow PENNY QUIZ - REASONING (Part 2)      posted 03-14-2010
4. After soaking the penny in question 2 in hydrochloric acid for two days, Raquel found that the zinc had all disappeared. She carefully washed and dried what remained of the penny; it was a thin, copper shell. When she weighed it, she discovered that it was 0.07 gram. (Raquel had to estimate the answer because the balance was only calibrated in tenths of grams.)
a. (5) What percent of the coin remained?
b. (5) What percent of zinc reacted?
c. (5) What percent of the coin was zinc?
d. (5) How do these percentages (of zinc and of copper) compare to the percentages stated (and calculated) in question 2? ("The 1983 - current penny is said to be ______% Zn and ______% Cu. Raquel's results indicated the penny was _____% Zn and _____% Cu. Based on these results Raquel's penny contained _________ (more/less) copper than was predicted from the data.")

ANS: (part a) You are told that 0.07 grams copper remains. To find the percent, set up a proportion:
100%/2.4 grams = x/0.07 grams.
Cross multipy: (100%)(0.07 grams) = (2.4 grams)(x)
Divide both sides by 2.4 grams to get the unknown "x" by itself.
(100%)(0.07 grams)/(2.4 grams) = x
The grams units cancel. Divide 0.07 by 2.4 and multiply by 100% to find 2.92% copper.

(part b) Since ALL of the zinc reacted, 100% of the zinc is gone.

(part c) Since 2.92% of the coin was copper, the zinc must be 100% - 2.92% or 97.08%. You could also set up another proportion: 100%/2.4 grams = x/(2.4 grams - 0.07 grams). Then (100%)(2.33 grams) = (2.4 grams)(x) and
(100%)(2.33 grams)/(2.4 grams) = x = 97.08%

(part d) All you had to do was to substitute the numbers you found in the spaces provided and compare the results: "The 1983 - current penny is said to be _97.5_____% Zn and __2.5____% Cu. Raquel's results indicated the penny was _97.08____% Zn and _2.92____% Cu. Based on these results Raquel's penny contained ___more______ (more/less) copper than was predicted from the data.")

5. After soaking in the HCl, some of the pennies looked silvery. Why?

ANS: Because some of the zinc that was inside the penny had to have formed zinc chloride. The zinc chloride was in solution. The amount of hydrochloric acid must have been very low, some of the water or HCl gas evaporated over the weekend, and the zinc precipitated out of solution. [All you needed to write was that the zinc from inside the penny somehow deposited on the outside.]

HOLLOW PENNY QUIZ - REASONING (Part 1)      posted 03-14-2010
Students, most of you did not do well on the "Hollow Penny" quiz, and I gave you a chance to improve your score by retaking it the following week. I thought that I explained everything clearly. When I asked you in class about your understanding, most of you were able to answer the questions satisfactorily. But when you retook the quiz, the scores were as low as ever. It is really necessary that you understand what to do to answer the questions; they are the type of questions that you will need to answer throughout your lives. I am reprinting the test in this Blog, along with the reasoning needed to answer the questions. Please study it well. If there is anything you do not understand, come see me. Although we are now heading into the ICS unit on biology, I will continue to give you questions like those on the Hollow Penny quiz until everyone scores higher.

ICS B -Chem Quiz - The Hollow Penny

1. Pennies minted from 1962 to 1982 were an alloy of 95% copper and 5% zinc.
a. (5) If one of the pennies weighs 3.1 grams, how many grams of copper is in it?
b. (5) How many grams of zinc is in the penny?

Ans: An "alloy" is a usually considered a mixture of two or more metals. Steel is a mixture of iron and carbon. Brass is a mixture of copper and zinc. Bronze is a mixture of copper and tin.

You are told that copper is 95% of the coin and zinc is the remaining 5%. The percentages must add up to 100%. This means that 95% of 3.1 grams is the amount of copper in the coin, and 5% of 3.1 grams is the amount of zinc in the coin. This means that the whole coin -- 3.1 grams -- represents 100% of the mass of it. To find the amount of copper, set up a proportion like this: 100%/95% = 3.1 grams/x. Cross multiply to obtain
(100%)(x) = (3.1 grams)(95%).
Then divide both sides by 100% to get "x" by itself:
x = (3.1 grams)(95%)/100%

Performing the arithmetic you find x = 2.945 grams of copper. Remember, the "%" signs cancel out and the units that are left are grams. Since 95% is a part of 100% -- it is LESS than 100% -- the number of grams you get have to be less than 3.1. If you get MORE than 3.1, you have done something wrong.

To find the amount of zinc in the penny, subtract 2.945 grams from 3.1 grams:

3.1 grams - 2.945 grams = 0.155 grams. Since there are two digits in the least accurate factor (3.1), we round off the answer to 016 grams of zinc.

2. Pennies minted from 1983 to the present consist of a core of zinc and a copper cladding. The penny weighs 2.4 grams. Zinc is supposed to be 97.5% of the weight of the penny. Copper is supposed to be the balance.
a. (5) What percent of copper is present in these pennies?
b. (5) What is the difference between an "alloy" penny and a "clad" penny?

Ans: You are told that zinc is 97.5% of the mass of the coin. To find the percent of copper in this penny, subtract 97.5% from 100% and get 2.5%. Notice that the question does NOT ask for the number of grams of copper; just the PERCENT.

In class you were told that an alloy is a mixture of metals. "Clad" means a coating or covering over something. For example, "When the house caught on fire, Jenny ran out CLAD only in her pajamas."

3. When zinc is placed in an acid, it reacts to form a zinc salt and a gas. The formula for the reaction of zinc with hydrogen chloride (which is found in hydrochloric acid) is:
Zn + 2HCl --> ZnCl2 + H2
a. (5) What is the name of the salt formed?
b. (5) What is the name of the gas formed?

ANS: You were told in class that the most common salt is table salt, or sodium chloride. It is composed of a metal (sodium) and a non metal (chlorine). You were told that any metal and non metal are called "salts." This is the name of a class of compound. So the salt formed from zinc and chlorine is named "zinc chloride." There is no sodium in the compound. You can see this by looking at the chemical equation. You were also taught that hydrogen has the symbol "H" and that two atoms of hydrogen form a molecule of hydrogen gas, (H2). [Please remember that on Classbuilder, I cannot make subscripts: The "2" in "H2" is a subscript meaning two atoms of hydrogen.

4. (See part 2)



What we have been doing in ICS class for 3 October 2009      posted 10-29-2009
We were studying plate tectonics and the joints between the plates. These are the source of volcanoes and earthquakes. When one plate is pushing against another, it is called a "convergent" boundary. Literally, one plate may be denser than the other, so it dives beneath the less dense one as it is pushed. This causes the less dense plate to buckle and form mountains. Further inland, the dense material resurfaces after being heated in the earth's mantle. It resurfaces as lava from volcanic eruptions. The second type of boundary is called "divergent." It is where the plates are moving apart and new crustal material is forced up, between them. This causes sea-floor spreading and occurs at deep ocean trenches. It is also occurring on land in the region of the world know as the "Afar Triangle." The third form of boundary is called "transverse" or "transform." It is where the plates are rubbing against each other, sideways. As this occurs, energy builds up until the plates finally slip. This results in earthquakes and earth movement. An example of a transform fault is the San Andreas. When it releases energy, the region is affected by large earthquakes.

Another source of damage during an earthquake is from "liquefaction." Ground water within about 30 feet of the surface rises, causing the soil above it to become fluid. This fluid is now less dense than structures built on the surface. Because it is less dense, the overlying structure tends to settle. This settling motion is uneven, resulting in structural damage to the buildings on the surface.

We also mentioned that the rock underlying the ocean is basalt. This is igneous rock that is characterized as smooth and small-grained, due to quick cooling, as occurs during a volcanic eruption. It is basic in chemistry. This rock is called "extrusive." In contrast, granite rock is more acidic. It is called "intrusive" because it is formed and remains underground where it cools very slowly and has time to form large crystals, as a result.

Also due to the cooling process, granitic rock splits horizontally while basaltic rock splits in vertical, or columnar, planes.


What we have been doing in ICS class      posted 10-16-2009
We are studying earth science. Most recently was a question relating to the density and mass of the earth's core. The problem is: The density of mercury is about 13.6. That means it is 13.6 times as dense as water. For example, a liter of water has a mass of 1,000 g or 1 kg so a liter of mercury would be 13.6 kg. The density of iron is 7.67. What is the ratio of the density of mercury to the density of iron?

Earths inner core is believed to be 2400 km. The core is believed to be solid iron. Around the inner core is the outer core and it is believed to be molten iron. The diameter of the outer core is believed to be 7000 km. Taken together, what is the mass of the inner and outer core in kg? The formula for volume of a sphere is V = 4/3 Pi r^3 where "r^3" means radius cubed.

If the outer core was mercury, not iron, what would its mass be, in kg?

How do you solve this? What does "ratio" mean? What is the relation between "diameter" and "radius?' Be sure to use conversion factors from g/cc to kg/cu. km. (1,000,000 cc = 1 cu. meter; 1,000,000,000 cu meter = 1 cu km)



This is what we have been doing in CHEMISTRY      posted 10-16-2009
Since we do not yet have books issued, we have been using teacher's notes and a copy of the text projected onto the screen in our room. We started to cover vocabulary terms used in basic chemistry including "reactant," "product," "chemical," "states of matter," and "chemical reaction." We discussed and I illustrated reaction types, such as "double displacement," "single displacement" and "synthesis" reactions. We said that reactions resulted in a change of energy levels that could be observed by (for example) change in pH, color, temperature, and state change (liquid to solid, solid to gas, etc.). Reactions that release energy are "exothermic." Those that take energy in are "endothermic." I gave a homework assignment asking students to place in an empty, plastic water bottle, a piece of steel wool, as from a well-washed steel scrubbing pad (remove as much soap as possible). Then, cap the bottle and let it sit for a couple of days. Report on what happened.

We also discussed the history of chemistry. The conflict between Democritus and Aristotle about "basic units of matter" was described. Also, how John Dalton found in 1806 that elements were unique substances, not just "earth, wind, fire and water" as had been expounded by Aristotle.

We are still learning about units of measurement including the prefix "kilo-," "milli-" and how to interconvert them.


WHAT WE ARE DOING IN ICS!      posted 10-12-2009
PLACE AGE OF EARTH, WITH MOVEMENT OF TECTONIC PLATES, ON BASIS THAT STUDENTS CAN UNDERSTAND.

1. On a map of the US, find San Francisco, CA, and New York City, NY.
2. Draw a straight line between these points.
3. The distance between SF and NYC is 2640 miles. Let this represent the age of the earth, about 5 billion years.
4. Teacher reads from book "Basis of Human Evolution" and identifies points on the map along the line representing milestones in the history of the planet.
5. Student is to scale the time in terms of miles traveled, about 1 mile (5280 ft) represents 2 million years.

After doing this, students see that the breakup of the super continent Pangea, occurred within 110 miles of the present (about 0.4 inch on the map). We changed the scale to amplify the view:

1. Find Victoria, British Columbia, and Jacksonville, FL, on the map.
2. Draw a straight line between these points.
3. The distance between Victoria and Jacksonville is about 3134 miles and represents 250 million years.
4. Plot the center points of the Permian (250M), the Triassic (200M), Jurassic (135M) and the Cretaceous (65M) years before present on the map.
5. Measure the length of the line, in cm.
6. Identify features of the land masses associated with each of these eras.
7. Write a paragraph about each era, comparing the changes.
8. Write about how the changes occurred, according to the text.

Students need to know that the time, in terms of distance, can be found by simple ratios or proportions. Thus: 250M/225M = 22cm/x. Solving, x = 19.8 cm.

Semester Project      posted 07-31-2009
When you write your research report, make sure you have all of the following parts:
0. Title with your name
1. Summary
2. Statement of purpose
3. FULL description of your research
4. What you learned
5. What are your conclusions
6. References

Report should be typed. Proof-read the report. No misspelled words or grammatical errors. References need to be comprehensive and complete. Make sure I have a draft or outline by Saturday night, 1 August 2009. Send by email if at all possible; if not then turn in as print on Monday.

-- St. Ern

what we did in class 30 July 2009 (continued)      posted 07-31-2009
A better way of seeing when the reaction between bicarb and acid is complete is when CO2 bubbles stop being produced. Then, you need to evaporate the solution to dryness. Except if you do it all the way on a hot plate, you will burn the acetate salt. When it is almost dry, but you have some liquid, put the beaker in the microwave for 30 seconds at a time. When dry, the salt is fluffy and has a slightly waxy feel.

Next, add 25 ml of water to a 100 ml beaker. Add about 100 ml of water to a larger (e.g. -- 250 ml) beaker. Put the larger beaker on the hot plate. Put the smaller beaker in it. This makes a double-boiler and assures that the temperature of the 25 ml of water will not be higher than the boiling point of water. When the water in the outer beaker is boiling, add the sodium acetate salt little by little until no more will dissolve to the inner beaker. At this point, you have a supersaturated solution. Take the smaller beaker out and let it cool. You can put it in another 250 ml beaker with cool water in it to chill it faster. If it remains fluid at room temperature, you probably have done everything right. Then, add a crystal of sodium acetate. It should start to crystalize and will release heat. If so, reheat the beaker (in the boiling water bath -- 250 ml beaker) to dissolve and pour into a pouch. Add the stainless steel initiator strip and seal the pouch. Now, when it cools, you should be able to flex the stainless steel and see the sodium acetate crystallize with release of heat.

-- St. Ern

what we did in class 30 July 2009      posted 07-30-2009
Today we learned about solutions. Specifically, we learned about making a supersaturated sodium acetate solution. The chemical equation for the reaction between acetic acid (which is 5% in the vinegar that we used) and sodium bicarbonate produced sodium acetate, a salt, in addition to the carbon dioxide that we studied last week, and water.

The reason we are using sodium acetate is because it stays fluid, even though you would expect it to crystalize when its solubility limit is reached. Crystallization will occur if a "seed crystal" is dropped into the solution, or if the system is disturbed in some other way. Then, heat is released as the crystals grow. The heat release is enough to allow sodium acetate to be used in hand warmers. (They can be "recharged" by placing in boiling water for a few moments.)

The hand warmers are made by sealing the supersaturated sodium acetate in pouches made from "lay-flat tubing." I brought an Impulse sealer for this purpose, and tubing. To activate the change from fluid to solid, a small strip of stainless steel sheet is sealed in the pouch with the solution. When the strip is flexed, it creates "nucleation sites" for crystallization to occur.

The following information was provided as a note:

Heating pad
A hand warmer containing a supersaturated solution of sodium acetate which releases heat on crystallization
Sodium acetate is also used in consumer heating pads or hand warmers and is also used in hot ice. Sodium acetate trihydrate crystals melt at 58 °C, dissolving in their water of crystallization. When they are heated to around 100 °C, and subsequently allowed to cool, the aqueous solution becomes supersaturated. This solution is capable of supercooling to room temperature without forming crystals. By clicking on a metal disc in the heating pad, a nucleation center is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is exothermic, hence heat is emitted.[2][3][4] The latent heat of fusion is about 264–289 kJ/kg.[5] Unlike some other types of heat packs that depend on irreversible chemical reactions, sodium acetate heat packs can be easily recharged by boiling until all crystals are dissolved. Therefore they can be recycled indefinitely.[6]
Preparation
Sodium acetate is inexpensive, and is usually purchased from chemical suppliers, instead of being synthesized in the laboratory. It is sometimes produced in a laboratory experiment by the reaction of acetic acid with sodium carbonate, sodium bicarbonate, or sodium hydroxide. These reactions produce aqueous sodium acetate, and water. Carbon dioxide is produced in the reaction with sodium carbonate and bicarbonate, and it leaves the reaction vessel as a gas (unless the reaction vessel is pressurized).
CH3–COOH + Na+[HCO3]– _ CH3–COO– Na+ + H2O + CO2
This is the well-known "volcano" reaction between baking soda and vinegar. 84 grams of sodium bicarbonate (baking soda) react with 750 ml of 8% vinegar to make 82 g sodium acetate in water. By boiling off most of the water, one can refine either a concentrated solution of sodium acetate or crystals.

I also gave you the following question to think about:

Given that the solubility of sodium acetate (Molar mass=82g/mol) is 76 grams per 100 grams of water.?
What is super saturated?
a) 8.5 moles of sodium acetate dissolved in 1L of water
b)1.8 moles of sodium acetate dissolved in 300 ml of water
c)5.5 moles of sodium acetate dissolved in 500 ml of water
d) 1.2 moles of sodium acetate dissolved in 200 ml of water
e) all of them

The reason for this question is to help you think. To answer the question, you need to calculate how many moles of sodium acetate will saturate 1000 grams of water. (Since 1 gram of water occupies a volume of 1 ml, we are determining how many moles of sodium acetate it takes to saturate a liter of water.) Then, you need to see which answer results in MORE sodium acetate in the water (in other words, "supersaturated").

How do you know the amount of sodium acetate to make? Based on experiments I did today, you should have about 25 ml of supersaturated solution in a pouch about 4 inches long. Use the answer to the problem, above, to guide you to determine how much sodium acetate you need for 25 ml. Set up a "proportion" equation as I showed you in class. Then, use the concept of stoichiometry (i.e. -- mole ratio) to determine how much bicarbonate of soda you need to produce it, and how much acetic acid you need to react with the bicarb. Remember, there is only 5% acetic acid in vinegar, so you need to calculate how much vinegar to use.

Once you have reacted the acetic acid and bicarb, you will see a clear solution. Remember though, that some bicarb is soluble in water so you need to add enough acetic acid to react with it, as well as the undissolved bicarb. You can't just look for a clear solution. (continues above)


What we did in class 27 July 2009      posted 07-28-2009
Today we focused on the carbon dioxide evolution lab. Students calculated how much vinegar (containing 5% acetic acid) did it take to react with a weighed amount of bicarbonate of soda. The bicarb was put in a flask and the vinegar was put in a balloon. The balloon was fastened to the flask and the vinegar tipped into it. The carbon dioxide evolved inflated the balloon. The students determined what the volume was of the balloon. From the volume, they determined how much bicarbonate had actually reacted and calculated a yield of actual to theoretical. Formulas used were:
1. Gross weight - tare weight = net weight
2. moles = mass (in grams) / atomic weight (sodium bicarbonate)
3. Stoichiometric ratio bicarb to acetic acid determined.
4. grams acetic acid needed = moles x atomic weight of acetic acid.
5. weight of acetic acid in grams x 100%/5% = grams of vinegar needed
6. grams vinegar = ml vinegar
7. balloon circumference (C) = Pi x diameter (d)
8. d = 2 radius (r)
9. Volume of balloon (V) = 4/3 x Pi x r(exponent 3)
10. moles CO2 = P x V/R x T where R = gas constant (0.082 liters.atm/mol.K) and T is temperature in Kelvins
11. K = oC + 273.15
12. mole ratio CO2:NaHCO3
13. moles NaHCO3 x atomic weight NaHCO3 = grams NaHCO3 actually reacted
14. grams Actual / grams used in equation 1 x 100% = yield

You were told to save the solution that results. It should be clear. If not, it means that some of the bicarb was left unreacted. The solution, now sodium acetate, is something that we want to use in our study of solutions. Specifically, when sodium acetate is in a "supersaturated solution," meaning there is more sodium acetate than should actually be capable of being dissolved, and a "seed crystal" is injected, the solution will crystalize and release heat. It is packaged and used as hand warmers. I would like to set you up to make hand warmers by evaporating the solution you have. I need something to activate the solution, which is what I am now looking for. Commercial warmers use a thin, stainless steel disk.

Many of you need practice solving problems. I'm giving you a few (below) to practice on:

1. A "molar solution" is made by dissolving one mole of a substance in water, then topping up to 1 liter. The concentration is thus one mole per liter. What is the concentration of 4 grams of table salt, sodium chloride, in one liter of solution?

2. Hydrochloric acid, HCl, is typically used at a concentration of 1 Molar, or one mole per liter of solution. How many grams of HCl is needed to make a 1 Molar solution?

3. Concentrated hydrochloric acid is 37.5% by weight. It is made by bubbling HCl gas through water until the water is saturated. How many grams of HCl gas are in 1000 grams of concentrated HCl acid? How many moles is this?

-- St. Ern

What we did in class 22 July 2009      posted 07-22-2009
We studied the meaning of the gas laws in some detail. Robert Boyle discovered the relationship between pressure and volume. He found that as you increased the pressure on a fixed amount of gas, the volume decreased, and vice versa. In other words, pressure is inversely proportional to volume. That is, P α 1/V. As an equation, this can be written as PV=K where K is a constant. Then, the French scientist Jacques Charles, while working for the Montgolfier brothers to help them with their hot air balloon, discovered that volume of a fixed amount of gas is directly proportional to temperature. That is, V α T. As an equation, this is V/T = K where K is a constant. And another Frenchman, Joseph Gay-Lussac, found that pressure of a fixed amount of gas was also proportional to temperature. That is, P α T. As an equation, this is P/T = K. We demonstrated Boyle's law with a plastic syringe and mini marshmallows. As pressure was applied, the marshmallow (inside the syringe) "shrunk." When the plunger was pulled back, air inside the marshmallow caused it to expand. We demonstrated Charles' law by fitting a balloon to a flask and heating it. As the air was heated, the air inflated. When we added a small amount of water and heated it, the steam inflated the balloon quite a bit. After the water had all evaporated, the temperature of the steam continued to increase and the balloon inflated even more. For considering Gay-Lussac's law, we discussed what happened when an aerosol can of hair spray was used. It takes energy to expand and that energy comes from the molecules inside the can. Consequently, as the container valve is operated, the spray leaves it and heat is removed from the rest of the spray in the container, cooling it. This is how air conditioners work, too.

The three laws were combined in the -- logically enough -- "combined gas law,"
P₁V₁/T₁ = P₂V₂/T₂. This was based on the fact that PV/T = a constant, so if the same amount of gas has any condition changed, the other conditions will adjust to maintain the constant.

The combined gas law says that for a fixed amount of gas at a given pressure, temperature and volume, if you change anything, at least one other condition will change. For example, for a gas initially at 1 atmosphere pressure (same as 14.7 pounds per square inch, or 760 mm Hg, or 760 torr), occupying 1 liter volume, and at zero degrees Celsius, if it is warmed by 10 degrees, but the container volume is kept constant, then the pressure will go up. If the container is allowed to expand, the pressure will stay constant.

Since PV/T = constant = K, a good question is "What is the nature of the constant? Just what IS 'K'?" By specifying the conditions to apply to just one mole of gas, we can explore this point. Through experiments it was discovered that one mole of gas occupies 22.414 liters at standard temperature and pressure, STP. What is STP? It is a pressure of one atmosphere at zero degrees Celsius. Let K =nR where "n" is the number of moles and R is titled the "Gas Constant." Then PV/T = nR. This is usually written "PV = nRT." Here, we rearrange to solve for R. That is R = PV/nT.

By the way, T is in units of Kelvins, or K. This unit was named in honor of William Thompson who was dubbed "Lord Kelvin" due to the importance of his discovery. He found absolute zero, the temperature at which motion stops. It is 273.15 below zero on the Celsius scale.

So, to solve the ideal gas law for R we have: R = (1 atm)(22.414 liters)/(1 mole) (273.15 K).
This yields R = 0.0802 liter ‧ atm/mole ‧ K.

Clearly, if you use different units for the volume or pressure, the value of R will change.

Importantly, when you are given problems, you can generally just plug in the appropriate values to solve them.

FOR TOMORROW: We will explore the experiment by Lord Kelvin to find absolute zero. We will examine how the volume of a gas changes with temperature, and then extrapolate on a graph to the intersect with the temperature axis. That intersect represents absolute zero.

REMINDERS:

1. Have your class notes ready to hand in so I can grade them for your three-week report.
2. You will have another on-line quiz over the weekend. It will cover the gas laws and the barometer.
3. If you can finish the absolute zero experiment on Thursday, I'll have you do another one on Friday involving calculation of the amount of reactants and products from the volume of a gas produced in the reaction.

Any questions, send me email.

--St. Ern

What we did in class 21 July 2009      posted 07-22-2009
Today we continued exploration of Boyle's law. Here is what we did: We put mini marshmallows in a 60 ml syringe. When we put our thumbs over the nozzle and pressed on the plunger, the marshmallow shrank. This had to be because the marshmallow was full of air. When we pulled a vacuum on the syringe, the marshmallow grew larger. because the air in it expanded. This really demonstrated the inverse relation on a fixed amount of gas by volume and pressure. If the pressure goes up, the volume does down, and vice versa.

Students were asked to write up a paragraph reflecting their understanding of this principle.

Then we explored pressure itself. We made a water barometer. Students had to understand that mercury, used in barometers since the time of Torricelli, are prohibited in schools. Mercury, being 13 times as dense as water can be used in a glass column 760 mm long to measure the pressure of the atmosphere. In other words, a column of mercury 760 mm long will balance the pressure of the atmosphere. You learned that the weight of a column of air one inch square, from sea level to the stratosphere weighs 14.7 lbs. We call that air pressure and it is stated as lbs per sq. inch. Since we can't use mercury, we used water. Students found that the column of water required to balance the atmosphere was about 32 feet. (760 mm x 13 /(25.4 mm per inch x 12 inches per foot). We took a length of plastic tubing 35 feet long, filled it with water and hung it from the 3rd floor landing. The top was sealed and the bottom was in a bucket of water. The water column in the tube fell to 32 feet, creating a vacuum in the top of the tube. The students were told to follow a specified report format.

We then started talking about Charles' law which relates temperature and volume. The students saw a demonstration of what happens when a balloon is fitted to a flask, and the flask is heated. The air inside the flask expands, forcing the balloon to inflate. When water is put in the flask, the balloon expands even more as the water is vaporized.

Students had a homework assignment to express the temperatures 212, 32 and 800 degrees F in Kelvins. They were shown the formulas: K = degrees C + 273.15; degrees C = (degrees F - 32) x (5/9).

Tomorrow we will continue with Charles' law, solving problems. We would also like to do a lab on finding absolute zero.

-- St. Ern

What we did in class 20 July 2009      posted 07-20-2009
The results of the quiz on moles, stoichiometry and balancing equations was pitiful. First, only about half the students bothered to take the quiz. Second, it was clear from the answers that most students didn't do more than guess. I scolded you for your poor effort and gave you one more chance: take the quiz over, today. I'll take the higher grade for the record.

Your homework is to study ch. 12.1 about gases. We started on this unit in class today. I described the work by Robert Boyle leading to Boyle's law. It states that the pressure of a gas and its volume are inversely proportional. This can be written as P = 1/V. It means that if you change the pressure on a fixed amount of a gas, the volume changes; conversely, if you change th volume of a fixed amount of gas, the pressure changes. Pressure goes up, volume goes down.

To illustrate this, I provided you with plastic syringes to experiment with. You saw that pressing the plunger increased the pressure as the volume decreased, and as the pressure decreased, the volume increased. (And several of the syringes walked off by themselves. Ms. Lepisto returned one confiscated from a student.)

You were to write a paragraph in your notes (which will be collected and graded this Friday) about Boyle's law. You were given a problem: If the volume of a cylinder is 760 cc, and the pressure is 1-atm, what is the pressure when the volume is compressed to 10 cc? After solving the problem using the relation P(sub1)V(sub1) = P(sub2)V(sub2) by rearranging to solve for P(sub2), you were asked to express the answer in lbs/sq. in., as "14.7 lbs/sq. in. = 1 atm pressure).

I intend to buy plastic tubing today, enough to make a water barometer. I explained that Torricelli found that a column of mercury 760 mm long balanced the pressure of air at sea level. Since mercury is banned in school, we can make a barometer with water. Since mercury is 13 times as dense as water, it means we need a column of water many feet long to balance the pressure of air. I asked you to solve this by multiplying 760 mm x 13 and dividing by 25.4 mm/inch and 12 inches per foot. (What is the answer?)

Tomorrow, we will fill a tube sealed at one end with water and see how long the water column is.

NOTE: Use a new lab booklet for the next experiment. Use note paper for class notes and homework. Make sure you do the assigned readings.

-- St. Ern

What we did on 15, 16 July 2009      posted 07-16-2009
There was no blog for the class for yesterday; I was at a meeting discussing some of the concerns besetting America and what we can do about them.

I taught you about "yield" from a chemical reaction. Basically, it means the amount of product you actually got compared to what you would expect based on the chemical reaction. For example, we burned a piece of magnesium to produce magnesium oxide. The reaction is:

2Mg + O(sub2) --> 2MgO

If we started with 0.5 gram of magnesium, how much MgO should we get?

Use the mole equation to determine: moles = mass / atomic mass.

The mass is stated. Get the atomic mass from the periodic table: 24.

Then the number of moles is 0.5g / 24 = 0.0208

You can see from the equation that for every atom of magnesium reacted, one molecule of MgO is formed. Thus, 0.0208 moles of magnesium should produce 0.0208 moles of MgO. To find the number of grams of MgO, rearrange the mole equation to solve for mass:

mass = (moles)(atomic mass)

Find the atomic mass of MgO by adding the atomic weight of magnesium and of oxygen, or 24+ 16 = 40. Then, multiply 0.0208 x 40 = 0.833 gram.

But is that really how much MgO was recovered? No, because some was lost as a coating on the tongs I used to hold the magnesium strip and more was lost as a fume. (I showed you what happened if we inverted a beaker over the burning strip of magnesium: the fume coated the walls of the beaker so we collected more than if we just burned it in the open air. You saw that the burning it beneath the mouth of the beaker starved it for oxygen and the combustion stopped.)

I told you to weigh a beaker before the experiment. This gave you a "tare" weight. Then, when you burned the magnesium strip, you were to collect the resulting MgO in the beaker as it fell off the burning strip. Then you weighed the beaker with the MgO in it. This gave you a "gross" weight. You subtracted the tare from the gross to get the "net" weight of the MgO. This weight would be less than 0.833 gram because of the losses I discussed above. Let us say the gross weight was 108.52 grams and the tare weight was 108.1 grams. Then the amount of MeO you recovered would have been 0.42 grams. The yield, or "percent recovery" is the amount recovered divided by the expected amount times 100% or 0.42/0.833 x 100 = 50.4%.

Even if you had some difficulty with this, you could still use the amount of MgO actually recovered to determine how much MgCl(sub2) you would produce in the next step. The reaction is:

MgO + 2HCl --> MgCl(sub2) + H(sub2)O

You know how much MgO you recovered. From that determine the number of moles: it is 0.42/40 = 0.0105 in this example. Then, inspect the BALANCED equation. You can see that for every mole of MgO, you produce one mole of MgCl(sub2). Therefore, the number of grams of MgCl(sub2) is:

(0.0105) x [(24 + 2x35) = 0.987 grams.

After you evaporate the water from the beaker, let us say you reweigh it and find the gross weight is 108.6 grams. This means the amount of MgCl(sub2) in the beaker is 108.6 - 108.1 = 0.5 grams. What is the yield of MgCl(2)? It is 0.5gram/0.987gram x 100% = 50.66%.

You need to find how much magnesium you have at the end of the reaction (in the MgCl(sub2)) compared to what you started with. To do this, find the fractional amount of magnesium by dividing its atomic weight (24) by the total weight of the magnesium chloride (94). Then multiply that fraction by the amount of MgCl(sub2) recovered: 24/94x0.5gram = 0.13 gram. Compare that to the starting amount of magnesium, 0.5 gram. What is the yield? It is 0.13/0.5 x 100% = 26%

REMEMBER THAT YOUR REPORT IS DUE TOMORROW, 17 JULY!!!!

After discussing the reaction, I taught you the algebraic method to balance equations. I gave you some problems to solve in class and I promised to give you more to practice at home. Here are four more:

1. Al + CuO --> Al(sub2)O(sub3) + Cu

2. Fe(sub2)(SO(sub4))(sub3) + KSCN --> K(sub3)Fe(SCN)(sub6) + K(sub2)SO(sub4)
NOTE: In the first term, there is a sulfate group (SO(sub4)) taken 3 times.

3. CaCl(sub2) + AgNO(sub3) --> AgCl + Ca(NO(sub3))(sub2)

4. C(sub6)H(sub5)COOH + O(sub2) --> CO(sub2) + H(sub2)O

THESE PROBLEMS WILL BE DUE TOMORROW, TOO.

The agenda is for us to get started on the kinetic theory of gases and the gas laws tomorrow. I am planning on two labs for you next week. YOUR NEXT QUIZ WILL COVER STOICHIOMETRY, MOLES AND BALANCING EQUATIONS. IT WILL BE ONLINE AND WILL BE DUE SUNDAY SO YOU WILL HAVE THE WEEKEND IN WHICH TO TAKE IT. IF YOU BALANCE THE EQUATIONS GIVEN AS HOMEWORK, THE QUIZ SHOULD NOT BE A PROBLEM FOR YOU.

As always, if you run into problems, send me email.

Daisy, thanks for settling down and paying attention.

--St. Ern






What we did on 14 July 2009      posted 07-15-2009
Today we learned how to write a lab report. We made lab notebooklets in which to write up the report on the first experiment, "Combustion of Magnesium and associated reactions.' Students were provided with a data page that identified what they were to look for. The data page is:

COMBUSTION OF MAGNESIUM RIBBON AND ALLIED EXPERIMENTS

1. Weigh a portion of magnesium ribbon. About 0.5g is enough. Record the weight.
2. Weigh a clean beaker. Record the weight.
3. Hold the magnesium with tongs.
4. Ignite the ribbon over a burner; hold it over the beaker to catch the residue of combustion.
5. What is the chemical equation that describes the combustion? Write and balance the equation.
5a. How many moles of magnesium did you start with and how many moles of magnesium oxide resulted?
6. Weigh the beaker and combustion product. This is the "gross weight." Subtract the weight of the beaker (the "tare weight") from the gross. This gives the "net weight." The net weight is mass of the magnesium oxide collected.
7. Based on the reaction equation, how many grams of magnesium oxide did you expect? How much did you actually obtain? What is the percentage recovery?
8. Write and balance the equation showing the reaction of magnesium oxide with hydrochloric acid to produce magnesium chloride and water.
8a. What is the mole ratio of magnesium oxide to hydrochloric acid?
8b. Based on the amount of magnesium oxide recovered, how much hydrochloric acid do you need to react with it?
9. Hydrochloric acid is hydrogen chloride dissolved in water. The concentration of hydrochloric acid that you will work with is 3.7%, the rest being water. How many milliliters of the dilute acid will you need to react with the magnesium oxide?
10. Add the acid to the magnesium oxide and stir or swirl to react. Use a glass stirring rod, if necessary.
11. When the reaction is complete, the solution should be clear. If you have undissolved residue, carefully add more dilute acid. Measure EXACTLY how much you are adding.
12. Using a hot plate or burner with wire gauze, warm the solution and evaporate to dryness. The result should be magnesium chloride crystals.
13. Cool and reweigh. Subtract the beaker tare from the gross weight to find the number of grams of magnesium chloride.
14. How many moles of magnesium chloride were recovered? How much was expected? How much magnesium was present in the material recovered? Compare the amount of magnesium recovered to the amount you started with as magnesium ribbon.

Classes started the lab. They will finish tomorrow, Wednesday.

Approximately half of the students took the online quiz "Atomic structure." Those who did not receive zero. Go to your page to see your score. The individual quizzes can be printed out if you want them.

-- St. Ern




What we did on 13 July 2009      posted 07-13-2009
We reviewed standards. You had standards 3a, b and c for classwork; standards 4d, e, f and g for homework. Today I placed you in seven groups and asked each group to explain what a particular standard meant. Some of you blew off the assignment. I could see this as I circulated through the room to work with you on understanding the meaning and application. I am glad that you enjoyed what Mr. Speer taught you. We are extending his lesson so you understand how to use the mole when you balance chemical equations and determine yields.

Tomorrow you will have a lab based on this. Starting with a piece of magnesium, you will ignite it. The result is magnesium oxide. How much magnesium oxide do you expect? How much do you actually obtain? Then, you will determine how much hydrochloric acid you need to react with the magnesium oxide to produce magnesium chloride. What is the other product? Finally, you will dry the result and calculate the yield. You need to understand how to determine the molar mass, number of moles and percentages. You will need to know how to use a balance, and how to work in the lab safely.

There may be a blog describing this experiment in prior years. You might scroll through the list and see.

-- St. Ern

What we did on 10 July 2009      posted 07-13-2009
We had classes reassigned. My Chem A&B class was cancelled because too few students were taking both chemistry A and B this summer. I inherited Mr. Speer's chemistry B classes, periods 1 and 2. We started reviewing where Mr. Speer left off. Students were given a copy of the course syllabus. Contact cards were issued and filled out. Students were given points for correctly filling out the cards. Those who did NOT follow instructions did not receive full credit. We started learning about balancing chemical equations. We'll continue on Monday. A quiz -- almost a duplicate of what Mr. Speer gave you -- is on-line and is due by Tuesday.

Remember to bring books, writing implements, etc., to school. Observe the dress code.

-- St. Ern

What we did on 9 July 2009      posted 07-10-2009
Confusing day! We reviewed the assessment quiz from the 8th. Then conducted a density lab. We'll look at what you did on 10 July. Then, we will be redistributing to other classes. I'm scheduled to take over chem B classes, both periods 1 and 2. Just have to wait and see what happens!

St. Ern

What we did on 8 July 2009      posted 07-08-2009
At 9 we went after books. The whole class went to the book room. We reviewed the material from 7/7 and you were reminded to give the "Tips for Parents" cards to your parents. I suggested that they place the cards someplace where they would be a reminder to ask you about school, every day. Some students turned in the emergency cards; others still have to turn them in.

You learned about "historical" chemistry. Who was John Dalton? Of Dalton's Laws, how many remain unchanged? When did he formulate his ideas? Who was Neils Bohr? What did he do? Remember, he was dyslexic and still accomplished much. We discussed atomic structure and the relative size of an atom. Quick! If the nucleus was the size of a marble, where would the first electron be? You learned about atomic number, atomic mass, protons, neutrons and electrons. You also learned how to find the number of neutrons when the atomic mass and atomic number were known.

We discussed how chemical formulas are written. For example, when ammonia NH3 (a gas) dissolves in water, it forms ammonium hydroxide, NH4OH. That compound ionizes to form NH4(positive) and OH(negative). They react with, for example, sulfuric acid, H2SO4 to form (NH4)2SO4 (where that "2" outside the parenthesis is also a subscript), and water.

We started discussing scientific notation, significant figures, dimensional analysis (or unit conversion factors), the meaning of the mole and Avogadro's number. I mentioned that one way of remembering Avogadro's number was to think of it as a telephone number: "Ava Gadro: 602-1023."

We saw just how big a number Avogadro's number was in comparison to the number of seconds since the universe formed `13.6 billion years ago: 4.688E17 compared to 6.02E23.

Manuel Panduro came up with a clever way to remember the rows and columns of the periodic table: "You climb a column, but run a row!"

You had a brief essay question to ponder: "From your 'prior knowledge,' of chemistry and what you have been learning in this class, suggest a way to organize elements in some way OTHER than the current idea of the periodic table."

For homework, you were asked to develop your name (or other word) using periodic table symbols, and to send them to me at "abinc@aol.com." I said I would print them onto thermal paper so you could transfer them to a garment.

Finally, we began to review the text, ch. 1 and 2. You were asked to study the figures, the tables, the vocabulary and the highlighted words. REMEMBER TO BRING YOUR BOOK BACK TO CLASS EACH DAY.




What we did on 7 July 2009      posted 07-08-2009
Today we started by reviewing what we did yesterday, especially the description of how to write a lab report. We went over additional details of what to include and how to write it. Next, I gave out a questionnaire about student behavior and how I, as your instructor, can best help you. Your responses have shown me that some students can use assistance in special areas, or in special ways. I'll do what I can to help you.

I described how to use the www.classbuilder.com website (class page: sternchem), and displayed it on the screen so everyone could see it. Remember, you have an on-line quiz to take and it is due by 8 July 2009. I showed everyone how to access the website using their email address and the password (actually, a "passnumber.")

Next, you completed the "Hollow Penny" lab by reweighing your penny and subtracting that weight from the initial weight. This gave you the amount of zinc that reacted with the HCl to produce hydrogen gas (H2) and ZnCl2 (NOTE: I can't do subscripts with this program. You have to KNOW that the 2 in hydrogen and in chlorine means "2 atoms" of those elements.

We used this information in a discussion of density (density = mass divided by volume) and an introduction to the mole concept (moles = mass divided by atomic mass). I explained that the mole referred to a specific quantity, like a dozen means 12, and a pair means 2. I put the following words on the board for you to know: meniscus and stoichiometry. We also used the words divisor, density, limiting reagent, coefficient. (PLEASE LEARN THESE WORDS AND THEIR MEANINGS). You learned a little about the metric system, that 1 ml = 1 cubic centimeter (cc), and the prefixes: mili = 1/1000, centi = 1/100, and deci = 1/10. We gave examples like cent in century, or as in 1/100 of a dollar, and centavo, as 1/100 of a peso. Millennium has the root "mil" and means 1000, as 1000 years. Deci means "10" and is the basis of the decimal system.

I showed you how to solve problems using addition (decimal points line up) or subtraction, and multiplication (with a brief introduction to scientific notation). You learned that to divide numbers, the denominator (bottom number in a fraction) goes into the numerator (top number).

We modeled dilution of an acid. In particular, we had 37% hydrochloric acid (that is hydrogen chloride dissolved in water) and we diluted 20 ml of it to 100 ml with pure water. That is what we used in the penny lab. You solve it like this:

37% = 100 ml
---- ------
x 20 ml

Cross multiply and divide by 100 for x = (37%)(20ml)/(100ml) = 7.4%

You used the information on the weight of Zn that reacted with the acid solution to calculate the number of moles of zinc. From there, you calculated the number of moles of ZnCl2. Then you found the atomic weight of ZnCl2, multiplied it by the number of moles present and obtained the mass (in grams) of the ) ZnCl2.

Tomorrow we get our books and we will start on chapter 1. You already know a little about the periodic table from what we have done so far. Hopefully, we can make our notebooks tomorrow, too.







What we did on 6 July 2009      posted 07-06-2009
This summer school class is being conducted just a little differently from what you might have expected. Since all students in this class are taking chemistry A and chemistry B, I am teaching you "A" for 3 weeks, 4 hours per day, followed by "B" for the next 3 weeks, 4 hours per day. This "immersion" should give you a good opportunity to do very well in both parts of the chemistry course. I will be voluntarily providing a FIFTH hour of instruction each day from 12:20 to 1:20 PM. During this time, I will work with you on topics with which you may need help to really succeed in chemistry. You are NOT being forced to attend the fifth hour, but it is in your best interest to attend.

Today we:
1. Prepared a self-study questionnaire and guide. This guide reflects how you have been studying. It is what we call a "reflection." That means we thought about the question and wrote down the way it is for us now. You were asked to keep the guide. In a few weeks, we will revisit it and see if your study methods have changed (improved?) based on understanding how you can best study.

2. Made "notebooks." The notebooks are for use until we make more permanent ones. They involved folding a cutting a couple of pieces of paper to make an 8-page booklet. Always, always, always put your name, date and (when applicable) period/subject on the notebooks.

3. Read chapter 1 in "Cartoon guide to Chemistry." This chapter discussed the history of chemistry. Quick! What was the very first chemical reaction to impress our ancestors? (NOTE: The history of chemistry, even though very briefly presented in the "Guide," is something all chemistry students should know.)

4. Learned how to "preread." We will go into more detail when you get your textbooks, and practice summarizing from books, but until then, go over ch. 1 of the Guide again, tomorrow. This time, use the hints you learned from the "preread" sheet to take notes in your notebook on ch. 1.

5. Discussed how to write a lab report. There are 7 parts. These are (a) statement of purpose, (b) materials and equipment, (c) procedure, (d) results with data, etc., (e) error analysis, (f) conclusions and recommendations, and (g) references.

6. Had chance to start writing a lab report. You titled it "The Hollow Penny," which was great title. You learned how to use a triple beam balance to weigh a penny, then you learned the chemical reaction that would be involved (What was that reaction?) and you carried it out. You saw the reaction start and you understand that it will go overnight. You learned how to calculate dilution of an acid, and that the class of compounds called "salts" are composed of a metal and a nonmetal. You began learning symbols for chemical elements and that the symbols used today are nowhere as complex as the symbols used by early alchemists.

We also discussed how many elements the ancients thought there were (earth, wind, fire and water), and how they realized there was something missing -- something mysterious that they named the "quintessence." (You should define this, if you don't remember what we said in class.)

We played with syringes to learn about air pressure. (Darn. I meant to get some mini-marshmallows for you to see what happens as the pressure changes.... but there is another way to do it. I can use a "Cartesian Diver.")

We also started talking about how to balance chemical reactions and what happens when something is "oxidized," or burned. That led into the discussion of the different kinds of "airs" that Joseph Priestley discovered and we mentioned nitrogen, carbon dioxide, hydrogen and oxygen. Other elements we mentioned today were zinc, sodium, gold, potassium, iron, bromine, chlorine, fluorine and iodine. (Please make sure you know the symbols for these elements and compounds.) We said a few words about the "father" of the periodic table, Demetri Meendelev.

For tomorrow, we will finish the hollow penny experiment. You will need to dry and weigh what's left, then write up your report. We will go after books tomorrow and get started on the study of the PT in earnest. THERE IS A BRIEF ASSESSMENT QUIZ ON-LINE FOR YOU TO TAKE. IT EXPIRES ON 8 JULY SO MAKE SURE YOU GET TO A COMPUTER AND TAKE IT BEFORE THEN!

Sinerely,
--St. Ern





Cheating      posted 06-14-2009
On the chemistry exam for 29 May 2009, if your grade has a decimal point followed by two zeros (xx.00), then it means your exam was just like someone who sat next to you and suspect that you shared answers, or cheated. The grades were so low that I'm not bothering to give you zeros on the exam, but you should know that I'm not giving you the benefit of the doubt on your final grade. If you were within a point or two of a higher grade, I would give it; now, no way.

-- JLStern

Salt Dissolving Experiment      posted 03-06-2009
This note is about the salt dissolving experiment. The experiment was to see if a change in dissolving time occurred as more and more salt entered the solution. Three different water temperatures were studied; cold, room temperature and hot. Students added about 7 grams of salt to 100 ml of water, stirred until it dissolved and timed how long it took. They weighed the container of water before and after. The difference in weight was how much salt they had added. Then they repeated this with another approximately 7 grams, stirred, timed and weighed. They repeated it a third time. The results were to be graphed as the total weight of salt on one axis and the dissolving time for each salt addition on the the other axis. For example, let us say the first 7 grams took 50 seconds to dissolve, the second 7 grams took 62 seconds and the third took 72 seconds. The student would make marks at the intersection of 7 g and 50 sec, 14 g (7g +7g) and 62 seconds and 21 g (7g + 7g + 7g) and 72 seconds. This shows that as more salt is added to the solution, it takes longer to dissolve. Some students used three different temperatures of water and attempted to plot that data. That was incorrect and the data was worthless. They were to stay with the same water temperature; either cold, hot or room temperature. By comparing data between different groups of students, testing at different temperatures, the class was supposed to learn that hot water dissolved the salt the fastest and cold water the slowest.


     posted 11-15-2008
Description of how to rearrange equations to solve for unknowns.
Dear classes -- Chemistry, mainly-

Math is the language of science. Until you speak "Math," you will have great trouble in understanding science. And, you need science to graduate from high school, not to mention how useful it is in everything that matters to you in your world.

We covered simple fractions, percentages, decimal fractions and how to rearrange equations to solve for unknown variables. I have even listed a You-Tube link that shows how to rearrange equations. I urge you to go to this link (below) and watch the video.

Here are some simple steps to rearranging an equation to solve for an unknown.

1. Collect similar terms (i.e. -- all the known values on one side; the unknown that you are trying to solve for is on the other side of the equal sign.)
2. What you do to one side of the equation, you do to the other side.
3. If you are adding, then you subtract the term from both sides; if you are multiplying, then you divide, and so on.

Look at this example:

P1x V1 / T1 = P2x V2 / T2

This is the "combined gas law." It tells you that the pressure times the volume of a gas divided by the temperature is always equal to a constant value. The pressure times the volume divided by the temperature for the same gas at a different set of conditions must also equal the constant. Therefore, the two conditions can be set equal to each other. If the temperature has not changed, then T1 = T2 and they cancel out. That leaves P1 x V1 = P2 x V2. Let us say you know the initial pressure, P1, the initial volume V1, and the final pressure P2. Then we need to rearrange to solve for the new volume, V2. Let's see how:

P1 x V1 = P2 x V2
(P1 x V1 )/ P2 = (P2 x V2)/ P2

Since we are multiplying P2, we divide it to enable us to move it to the other side of the equation. The P2 in the numerator cancels with the P2 in the denominator on the right side. Rewriting:

P1 x V1 / P2 = V2

In words, "P1 times V1 divided by P2 equals V2."




Biology Assessment I notes      posted 10-24-2008
These are notes to assist the biology class to do well on the Standard Assessment Test, Study them carefully. Most are in the form of questions:

1. What are the following:
a. Viruses
b. eukaryotic bacteria
c. prokaryotic bacteria

2. What is an “organelle?” What do the following organelles do?
a. ribosome
b. mitochondrian
c. Golgi apparatus
d. nuclear membrane

3. What is the difference between eukaryotes and prokaryotes?
a. nucleus
b. protein coat
c. cell membrane
d. ribosome
e. ribosomal RNA

4. What happens during the dark phase of photosynthesis? What happens during the light phase?

5. What do each of the following do?
a. bases
b. sugars
c. fatty acids
d. amino acids

6. What is active transport? Does it require or give up energy?

7. What is facilitated diffusion? Does it require or give up energy?

8. What are the steps involved in protein synthesis? (I gave you an illustration of this.)

9. Why do different cells have or make different proteins?

10. What would produce an inactive protein that is smaller than it otherwise should be?

11. Beside structural functions, what else do proteins do?

12. What is a “codon?” Explain what a mRNA codon does or pairs with during translation.

13. Dr. Frankenstein has spliced plant genes for chloroplasts into the chromosomes of termites. His theory is that when the chloroplasts are exposed to sunshine, they will produce food for the termites so the insects will not need to bore into structural wood for food. Where can you find reliable information on risks or benefits of his idea?
a. T.V. news or radio talk shows.
b. Internet news and blogs, especially “stop.com” (Stall Termites On Photosynthesis)
c. Science journals where other researchers analyze Dr. Frankenstein’s work.
d. Igor, a spokesman for Dr. Frankenstein.

14. What are proteins composed of? Can different proteins (that is, different functions) contain the same number AND sequence of these components?

15. In class, you chewed a cracker until it tasted sweet. You learned that the enzyme “amylase” in your saliva broke the starch in the cracker down to simple sugars. What would taste sweet faster: chewing a whole cracker all at once, or nibbling a little piece? Why?

16. What precisely do ribosomes do? (Detailed explanation)

17. If you have a skin condition, some doctors recommend soaking in salt water? Why? On the other hand, what would happen if you soak in distilled water? What does this suggest to you about the balance of salts in or out of body cells? What would happen if we soaked a stalk of celery in salt water? In distilled water?

18. We demonstrated how DNA is transcribed to messenger RNA which then travels to the ribosome. At the ribosome, transfer RNA’s bearing amino acids bind to the mRNA bases such that a guanine on the tRNA binds to an cytosine on the mRNA, and an adenine on the tRNA binds to a uracil on the mRNA. It takes a set of three bases on the mRNA, called codons, to bind to three opposite bases on the tRNA, called anticodons. Find a genetic code chart in your book. If the anticodon is Adenine-Adenine-Adenine (abbreviated AAA), what amino acid is specified by the codon?

19. Antibiotics lose effectiveness when bacteria mutate. Surviving bacteria then grow to recolonize an infected site. If the genetic material (genome) of the original bacteria is a little different from the genome of the now resistant organisms, what does that tell you about mutations?

20. Sketch the process of protein synthesis starting with the double helix of DNA.

21. Sickle-cell anemia is caused by a mutation that changes the DNA sequence from CAT to CTT. Then, the mRNA codon sequence changes from GUA to GAA and the amino acid that is specified changes from Valine to what? Use the genetic code chart in your book to find out.

22. What is “genetic engineering?” What are some of the success stories due to genetic engineering?

23. What do the following organelles do?
a. nucleolus
b. ribosome
c. lysosome
d. mitochondrian

24. How important is it to be accurate when you observe science experiments?

25. When you study figures, understand them thoroughly before working on the problem that they serve to illustrate.

26. Viruses are a little like aliens in horror stories. Once they infect you, they can add their genetic material to your own. But they can lay dormant for years and, since their genetic material is mixed with yours, it can be transferred to subsequent generations. What does this tell you about trying to “breed” infection out of a plant or animal?





Great Early 20th Century chemists      posted 10-07-2008
Who are some of the "Greats" of early 20th century chemistry? Jonathan C. researched several as part of a class project. Here are his findings:

John Dalton- he is best known for his work in the development of modern atomic theory, and his research into colour blindness also known as Daltonism. a lunar crater was named after Dalton.

Albert Einstein- received the 1921 Nobel Prize in Physics for his services to Teoretical Physics and for his discovery of the law of the photoelectric effect. he is also known for his theory of relativity and mass-energy equivalence, E =mc ².

Wolfgang Pauli- found that the current idea that it was magnetic moment of the core of the atom that was responsible for the splitting of the electron energy levels pf the outer electrons was incorrect. proposing a new model, his famous exclusion principle.

Friedrich Hund- discovered an observational rule of atomic chemistry, Rule of Maximum Multiplicity. This rule is used in atomic chemistry, spectroscopy, and quatum chemistry.

Niels Bohr- developed the "planetary" model of the atom. The model introduced the concpet of electron motion to the atomic model.

Amedeo Avogadro- found a resolution to the confusion surrounding atoms and molecules. he believed that particles could be composed of molecules and that molecules could be composed of atoms.

J.J. Thomson- discovered an even smaller and more fundamental partical called the electron.

Dmitri Mendeleev- found that by listing elements in order of increasing relative , their properties recurred in a periodic pattern.He proposed the periodic law and arranged early versions of the periodic table.




Calorimetry      posted 08-11-2008
After reviewing just a few of the lab reports by the Chem A, Summer 2008 students, I realized that comprehension of what the experiment was and what it accomplished was missing. This note explains it and will be for future reference by students:

I. Purpose: To determine the heating value (calorie content) of various substances, especially foods.

II. Materials: 1. Known volume of water in 250 ml Erlenmeyer flask
2. Thermometer
3. Known mass of vegetable oil (approx. 2 grams)
3a Food-stuff or other combustible material (about 2 grams)
4. Watch glass
5. Cotton wick
6. Apparatus stand and flask clamp

III. Procedure: A. Introduction: The word calorimetry comes from the Latin word "Calor" meaning heat, and "-metry" meaning to measure. The method depends on burning a known mass of something as fuel and recording the increase in temperature of a known mass of water. The calorie is a unit of heat energy that is defined at the amount of heat required to raise the temperature of one gram of water (initially at 4 degrees Celsius) by one degree. Thus, ten calories is the amount of heat to raise ten grams of water by one degree, or one gram of water by ten degrees. Starting with water at its freezing point, it would take approximately 100 calories per gram to raise it to its boiling point. To evaporate water at its boiling point takes an additional 540 calories per gram.
B. Method: In this experiment, some students will measure the heat released by burning vegetable oil. Other students will use a small amount of vegetable oil (weighed) as a fuel to start another substance, such as a corn chip, etc., to burn. All materials are carefully weighed and the masses recorded in the student notebooks. In all cases, the results will be expressed as "calories per gram." The heat that is released by the combustion is used to raise the temperature of a known amount of water in a flask. The final temperature of the water in the flask is read and from it is subtracted the initial temperature. This temperature difference multiplied by the mass of the water in the flask represents the amount of heat liberated by the fuel in calories. (In the event the fuel is very energy-rich, or if too much fuel is used, the water in the flask may boil. In this case, the amount of liquid evaporated in grams must be determined (by subtraction from the amount initially present) and that difference must be multiplied by 540 calories to determine the amount of heat released by the fuel to vaporize the water. That amount of heat plus the amount of heat to raise all of the water to the boiling point from the starting temperature is the total heating value of the fuel.
C. Example: 50 ml of water initially at 22 degrees Celsius is heated by burning vegetable oil. The amount of oil initially present was 5 grams. When the experiment was stopped, 1.5 gram of oil remained and 10 ml of water had evaporated. What is the heating value of the oil?

IV. Results: Ans: From the statement of the problem, we know that 10 ml of water, or 10 grams, had been converted to vapor. Since it takes 540 calories per gram to evaporate at the boiling point, we know the amount of heat to evaporate the water was 540 cal/g X 10 g = 5,400 calories. We also know that we started with 50 ml (50 g) of water and this went from 22 degrees to 100 degrees, a difference of 78 degrees. We multiply 50 g X 78 degrees X 1 cal/degree/g = 3,900 calories. We add 3,900 calories + 5,400 calories to get 9,300 calories. The amount of oil that was burned was 5 g - 1.5 g = 3.5 g. Dividing 9,300 calories by 3.5 g yields a heating value of 2,657 calories per gram of oil.

V. Error Analysis: Some heat was lost to the surroundings because the experiment was not conducted inside of a thermally insulated calorimeter. To give support to the oil as it burned, a cotton wick was used. Combustion of the wick may have added a little energy to the water as it heated. Combustion of the oil was not complete. We know this because a layer of soot accumulated on the bottom of the flask. Had the oil burned completely, there would not have been the soot layer and more water would probably have evaporated.

VI. Conclusions: To a first approximation, this experiment allowed us to calculate the heating value, or enthalpy, of oil. Had we used a mix of oil and a food, we could have used the data to determine how much of the heat came from the food and how much came from the oil.

VII. References: Holt Chemistry







Extra Credit      posted 08-03-2008
A student wrote to ask if he could provide a Power Point presentation instead of writing a paper. Yes, this is certainly an acceptable format. I suggested in class that a written paper or a "hands-on" project were just two options available. A Power Point presentation is a great idea!

Also, some students were extremely comprehensive in their summaries for ch. 6. In some respects, they wrote TOO much. Nevertheless, I don't want to discourage you (them) from summarizing the text as they search out information. Consequently, I have awarded extra credit to those students who went "above and beyond" the assignment. Good for you!

Important: I observed that there was a direct correlation between the scores on quiz 4 and how thoroughly you summarized your chapter material. Students, this method WORKS! Those who shrugged off the assignment, well, you will likely have to repeat the class --- again.


Equilibrium experiment -- Chem B      posted 07-28-2008
Equilibrium
Scenario
You work for a company called, Merky Pharmaceuticals. Your team has been asked to give a presentation on how a new drug the company has developed. This drug helps to control the concentration of iron in the blood of people who have a genetic disease. The disease suppresses the protein that regulates blood-borne iron. Your team has been asked to present a 10 minute explanation of chemical equilibrium. Your audience is the stockholders. Most of them know little about chemistry except for the chemistry they took in high school.
Background
Many chemical reactions take place in our blood. We will look at the basics of two kinds of reactions that our blood performs every day: buffering and iron balancing. Buffers in our blood prevent our blood from becoming too acidic or too basic. When we exercise, for instance, the acidity of our blood tends to increase. If the acidity isn’t controlled, then all kind of nasty things can happen. Our blood contains chemicals that remove excess acids.
The amount of iron (in the form of iron ions) in our blood needs to be regulated chemically. We need just the right amount of iron to make hemoglobin that carries oxygen to every cell in our body. When the level of iron gets too high, chemical reactions remove iron from the blood. When the level of iron gets too low, other reactions occur that add more iron to our blood.
How can substances like acids and iron be removed? What does that mean? How can something as small as an ion of acid or iron be removed? (Very small tweezers?)
How can more iron be added to our blood? Do chemical reactions occur that release the iron trapped in substances in our body? How do these substances “know” when to release and when to capture the iron?
In this lab you will study a chemical law known as equilibrium. A French chemist by the name of Henri Louis Le Chatelier made sense of the rather complicated mathematics surrounding chemical equilibrium. In this lab you will see how equilibrium is applied in two chemical systems and use Le Chatelier’s Principle to interpret what you will experience.

Materials
For Part I - Per Group For Part II - Per Group
Quantity Item Quantity Item
1 dropper bottle Fe(NO3)3 (0.045M) 1 dropper bottle HCl (0.1M)
1 dropper bottle KSCN (0.002M) 1 dropper bottle NaOH (0.1M)
1 dropper bottle deionized water 1 dropper bottle acetate buffer
Small crystals of KSCN 1 dropper bottle bromcresol green indicator solution
Small crystals of Na2HPO4
1 24 well plate or spot plate
1 small plastic cup or 125mL beaker
1 scoopulas
1 beral pipet
1 plastic stirrer

Tasks
Part I: Can reactions go in reverse?
This lab will follow a format different from the format used in other labs. Begin by writing the names of the two ionic compounds used and write down the two kinds of ions in each of the two substances. Then read the directions at the right and write down your observations or responses on the left, as you go along step by step.
Part I
Name of Fe(NO3)3

Color: Name of KSCN

Color:





Step 1: Place 45 drops of the KSCN solution into the plastic cup. Place one drop of the Fe(NO3)3 solution into the plastic cup, and swirl the cup to mix. On the report sheet write down your observation. Your teacher will help you determine the chemical equation for the reaction.

Step 2: Use the beral pipet to separate the contents of the plastic cup into 4 wells of the spot plate. You want to separate the solution so that all the wells will look the same color. Don’t completely fill each well, and you may have some solution left over. Well #2 will be the reference, so that you can compare the color changes in the other wells to it.

Step 3: Add one or two tiny crystals of KSCN to well #1. Stir gently with a stirrer. Compare the color in well #1 to the reference well #2. Record your observation on the report sheet, and answer the question for step 3 on the report sheet.

Step 4: Add one drop of the Fe(NO3)3 solution to well #3. Stir gently with a clean stirrer. Compare the color in well #3 to the reference well #2. Record your observation on the report sheet, and answer the question for step 4 on the report sheet.






Step 5: Add one or two tiny crystals of Na2HPO4 to well #4. Stir gently with a clean stirrer. Record your observation on the report sheet, and answer the question for step 5 on the report sheet.
Clean out the well plate. Your teacher will give you directions.
Your teacher will give you directions for the debrief of Part I.

Ions present in solution

+ Ions present in solution

+ SCN-
Step 1: Observation:
Chemical Equation:
Step 3: Observation
Step 3: If cell #2 turned darker, more FeSCN2+ was produced. Which reactant, Fe3+ or SCN-, must have been present in excess in well #2 before you did step 3?

Step 4: Observation
Step 4: If cell #3 turned darker, more FeSCN2+ was pr

Summer chemistry reminder (week 2)      posted 07-17-2008
Hi !NAME!,

Remember, period 1. If you are going to claim extra credit for spelling names with the periodic table symbols, your images have to be emailed to me or transferred to my computer by Friday. Send them to abinc@aol.com. Remember also your homework and notebooks are due on Friday. Do not procrastinate!

Period 2 students, remember that your barometers are due on Friday for me to inspect. That means completely assembled with card pointer and calculations done to show what a change in pressure would read. Tomorrow -- Thursday -- we either fly a hot air balloon or study how to find absolute zero.

Yeah, yeah -- I know. Buzz Lightyear would say, "To absolute zero -- and beyond!"

About your Friday quiz: Period 1 will be heavy on the Periodic table and trends. I strongly advise you to answer the questions for ch. 4 (Periodic table) in your workbooks. Period 2 will be problem solving for gas laws and molarity. Expect something on partial pressure and Graham's law of diffusion. YOU WILL NEED YOUR SLIDERULES, SO GET COMFORTABLE USING THEM. Ditto scientific notation.

-- Mr. Stern

Summer school 2008 -- week 1 grades      posted 07-12-2008
Students received grades on four assignments this week. One was the quiz (worth 100 points), the second was homework (10 points), third was for notes (10 points) and the fourth was the lab (making and using the slide rule -- 25 points). You can check your progress by going to our website, log in with your email address and password. Students without email access need to see me. Thus, in the first week, there were 145 points available.

Most students did memorize the inspirational quote by President Calvin Coolidge. Regretfully, several did not. Remember, I am educating the WHOLE STUDENT, not just feeding you data. When I give an assignment, it is in your best interest to complete it. Similarly, several students did not complete homework, write up the lab or take notes. Those students lost points.

Something else that is abundantly clear is that most of my students are very, very poor in basic math. It is CRITICAL that your math knowledge be brought up to par, or you are likely to have many unnecessary difficulties in school and beyond. Starting immediately, I will hold a 30-minute remedial math tutorial daily, right after second period. Those students who were unable to answer the math problems on the first quiz -- and you know who you are -- are strongly urged to attend. (If you do NOT know who you are, I will be telling you privately!)

I also observe that several of my otherwise very capable students are terribly sloppy in their problem solving. In other words, they are disorganized. Consequently, they get lost when trying to solve problems. I urge THEM to attend my tutorial, as well.

Otherwise, I am generally pleased with how the first week went. There have been very, very few disruptions. The classroom has remained orderly and conducive to learning. Congratulations for helping to maintain the room!

Several of you have participated quite well. Your eagerness shows how much you want to learn. I am proud of you for that. Now, onward to week 2! We will study the periodic table in period 1 and the gas laws in period 2. We plan on having labs in both classes.

-- Jay L. Stern





New Biology topic -- ecology      posted 04-20-2008
Dear Biology class --

Your next assessment is in about four or five weeks. It will cover ecology and evolution. I want you to have the opportunity to study for this assessment so I am going to defer the study of genetics until after the assessment. Taking the topics out of the original order in which they were in will not harm your study. Genetics and heredity are certainly factors in ecology and evolution, but we do not need to study inheritance to understand them. (See standard 7, below, for example.) For your convenience I have listed the standards for ecology. Please make sure you write the standards in your notebooks:

Ecology

Stability in an ecosystem is a balance between competing effects. As a basis for understanding this concept:
1. Students know biodiversity is the sum total of different kinds of organisms and is affected by alterations of habitats.
2. Students know how to analyze changes in an ecosystem resulting from changes in climate, human activity, introduction of nonnative species, or changes in population size.
3. Students know how fluctuations in population size in an ecosystem are determined by the relative rates of birth, immigration, emigration, and death.
4. Students know how water, carbon, and nitrogen cycle between abiotic resources and organic matter in the ecosystem and how oxygen cycles through photosynthesis and respiration.
5. Students know a vital part of an ecosystem is the stability of its producers and decomposers.
6. Students know at each link in a food web some energy is stored in newly made structures but much energy is dissipated into the environment as heat. This dissipation may be represented in an energy pyramid.
7. * Students know how to distinguish between the accommodation of an individual organism to its environment and the gradual adaptation of a lineage of organisms through genetic change.

Here is a schedule of how we can proceed with our study:

Monday, 21 April --
1. (Copy standards during roll-taking.)
2. Watch the power point presentation
3. Break into Groups
4. Follow the assignment on power point
5. complete the homework assignment tonight.

Tuesday, 22 April
1. Meet in the Quad
2. Idenfity and count organisms in different areas of the school

Wednesday, 23 April
1. Invasive plant video clip
2. Causes of fluctuations in population sizes
3. Analysis of counting

Thursday, 24 April
1. Energy flows in ecosystems -- Sect. 13.3 in text
2. Food web, food chain

Friday, 25 April
1. Quiz
2. Element recycling; water cycle





Detailed answers to 7 March quiz questions      posted 03-08-2008
1. Why is carbon able to enter into chemical reactions with so many other elements?

We discussed this in class. Carbon has four electrons in its outer shell. It needs to gain four to complete the shell, or to lose four so the underlying shell is seen as complete. The energy to remove the four electrons is enormous so that doesn't happen (on this planet, normally, anyhow). Gaining electrons would give it a high negative charge (four electrons, remember) and the charge imbalance between the four positive protons and four more electrons results in a very unstable ion. So THAT doesn't happen. Instead, the carbon shares electrons covalently with other atoms. If it is in a salt like calcium carbonate, CaCOsub3, it is still covalently bound to the oxygen. "Sub" means the number following is a "subscript." Further, since there are four bonds to be formed, the number of combinations are large. Carbon can form single, double and triple bonds. When it bonds to other carbon atoms, it forms a crystal or lattice as in diamond or Buckyballs.

2. Why is water a liquid under normal atmospheric conditions?

Because although the hydrogen atoms in a molecule of water are covalently bound to an oxygen atom, they are not completely neutral in the sense that they are able to be attracted to the oxygen of an adjacent water molecule. This "hydrogen bonding" is strong enough to keep the molecules from drifting apart under normal conditions. In the atmosphere, when the air pressure is low, the molecules have enough energy to break free and form water vapor, or if heated, they gain enough energy to overcome the strength of the hydrogen bonds. If our plant had a lower atmospheric pressure, or was hotter, there would be more water in the vapor phase and less in the liquid.

3. Write and balance the decomposition of calcium carbonate:

This was discussed over and over in class. I'm really disappointed that more of you did not write the correct answer. When calcium carbonate is heated, it forms carbon dioxide and calcium oxide.

CaCOsub3 --> CaO + COsub2 .

4. Write and balance the following reaction: Complete oxidation of sugar (Csub6Hsub12Osub6) in the body to produce COsub2 and Hsub2O. Again, we went over this in class.

Csub6Hsub12Osub6 + 6Osub2 --> 6COsub2 + 6Hsub2O

5. Show the Lewis dot diagram for CaClsub2

You know that this means one calcium and two chlorine. You should know that chlorine has 7 electrons in its outer orbital and wants to gain one. You also should know that calcium has two electrons in its outer orbital and can lose them in forming a bond. Draw the dot diagram with chlorine on either side of the calcium like this: Cl : Ca : Cl Then, add two dots over each Cl, two under them and two between each of the atoms. Now, check: There are 16 electrons in all, seven from each of two chlorine atoms and two from the one calcium atom. That adds up to 16 electrons. Two between the Cl and the Ca (on each side) uses 4, leaving 12. Since we need the same number of electrons for each of two Cl, divide 12 electrons by 2 atoms and get 6 electrons for each Cl. Arrange the dots around the Cl. Then, stand back and admire your artwook.


Students, this material will be asked again. You need to learn it.

-- Mr. Stern




Chem notes - section 1      posted 02-18-2008
“TEACHING TO THE TEST”
THE ANSWERS ARE IN HERE SOMEWHERE.
YOU HAVE TO SEARCH FOR THEM
Section 1
On the assessment tests are multiple-choice questions. These tests are designed to be machine graded. Some students believe the test is something to be ridiculed. They don’t bother to even read the questions; just use a pencil to darken in the circles for answer A, B, C, or D for each question. Some students have developed this activity to an art form: if you look at their answer sheets from a distance, the darkened-in circles form designs. How nice.

What are the consequences of this behavior? For sure, it lowers the academic standing of the school. The students who do this know it hurts the school. Maybe they are doing it out of revenge – revenge that people want them to have an education. Or maybe they are doing it to spite the students who come after them. After all, they think of themselves as losers and don’t like the idea that someone else can succeed where they have already failed. The fact is, students who do well on assessment tests generally do better in life. Why anyone deliberately wants to fail is something I don’t understand.

The test rules don’t let teachers grab the papers from these misanthropes (if you don’t know the word, look it up in a dictionary!) and trash them. We are supposed to simply collect the papers and have them scored. Guess what? Starting now, I’m monitoring my students as they take the tests. If it seems like someone is just filling in the spaces without studying the questions – without trying to do the best they can – then I’m going to “out” them. I’ll post a list of their names, contact parents and counselors, and put notes in the cumulative file. If there is anything else I can do, I'll do it.

On the flip side of this particular coin is another choice. You can study the material presented here and pay attention in class. Do the homework assigned and stop goofing off. Then, answer the assessment questions to the best of your ability. Your grades will rise and you will “lose the loser” mentality.

You can consider this document – and those that come after -- as “notes.” You need to study them thoroughly. If you do, you will understand high school chemistry better than most college students understand freshman chemistry, and you should do really well on your assessment test.




Chem notes - section 2      posted 02-18-2008
Section 2
Let’s get started. In chemistry, the periodic table is THE central thought. It is more than just a chart hanging on a wall. The table lists the known elements in the order of increasing protons. Protons are particles in the nucleus of every atom of every element. Hydrogen has one proton and it’s atomic number is one. Uranium has 92 protons and its atomic number is 92. Do you see how this works?

Sometimes students confuse atomic number with “atomic mass.” Atomic mass is the sum of the mass of the protons AND the neutrons in an atom’s nucleus. Neutrons are neutral particles; they have no charge. Protons are about the same mass as neutrons, but they have a positive charge. To find the number of neutrons, subtract the atomic number – the number of protons – from the atomic mass. The difference is the number of neutrons.

What balances the charge on the protons? Electrons do. These are particles of very low mass, compared to a proton. In fact the mass of an electron is said to be 1/1730 of the mass of a proton. They carry a negative charge that is exactly equal to and opposite of the charge on the proton. The protons and neutrons are in the nucleus of the atom; the electron is some distance away from the nucleus. People like to think of the atom as a tiny solar system with the nucleus at the center, like the sun, with the electrons orbiting the nucleus like planets. It is not a totally accurate model, but it works. Importantly, it does imply that most of the mass of the atom is contained in the nucleus, just as most of the mass of our solar system is contained in our sun. Since the balance of the atom is mostly empty space, can you imagine how dense the nucleus must be?
Actually, the density of the nucleus has been calculated. The radius of the nucleus is estimated as between 1/10,000 to 1/100,000 the radius of the whole atom. The mass is about 10–24 grams. Doing the math suggests that the density of the nucleus is about 1015 grams per cubic centimeter.

Let’s put this into units you are more accustomed to. There are 453.59237 grams in a pound. There are 28,316.8466 cubic centimeters in one cubic foot. Doing the math
(1015 g/cc) x (28,316.85 cc/cu. ft.) / (1lb/453.59 g) = 6.24 x 1016 lb/cu. ft. The density of water is 62.34-lb/cu ft. so the nucleus is 10,014,163,340,000,000 times as dense as water.



Chem notes - section 3      posted 02-18-2008
Section 3
I mentioned that the periodic table is the central thought in chemistry. It was not always so. In the time of the Ancient Greeks, thinkers were already trying to understand the world around them. They came up with the idea that there were four elements – that is, four basic substances that made up everything about them. These four were earth, wind, fire and water. It is easy to see why they thought this: When something was burned, it produced ash, which certainly resembled the earth upon which they walked. And water appeared to be in bodily fluids, fruits and other liquids. Wind was the air they breathed and fire, why it was literally the stuff of life. Even the ideas of the philosopher Democritus, who said that all matter was composed of finite elements that he called “atomus,” did not conflict with the concept of four, basic substances.

But the concept of an element as a unique substance did not seem to have occurred to the Greeks, nor to people for thousands of years. They headed down the wrong path of science, trying to “transmute” common metals into gold, for example. To them, this exercise in futility made perfect sense. If there were only four elements, then proper blending of various substances that contained the elements should produce the desired result. It never did. But what the early experimenters did accomplish was to build up a body of knowledge of what did not work. Further, they discovered how to isolate various substances and what the properties of those substances were.

The man who brought some order to the confusion was John Dalton. In 1802 he published work that has come to be known as “Dalton’s Atomic Theory.” There were five main points:
-Elements are made of tiny particles called atoms.
-All atoms of a given element are identical.
-The atoms of a given element are different from those of any other element; the atoms of different elements can be distinguished from one another by their respective relative weights.
-Atoms of one element can combine with atoms of other elements to form compounds; a given compound always has the same relative numbers of types of atoms.
-Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process; a chemical reaction simply changes the way atoms are grouped together.

Although portions of Dalton’s work has been modified based on later discoveries, his ideas serve as a guide to chemistry even today. For example, we retain the idea that elements are the smallest part of a substance that retains its unique properties. Of course, John Dalton knew nothing of subatomic particles, isotopes or radioactive decay. Nevertheless, his ideas served as a roadmap for later scientists, taking them off of the dead-end path originally charted by the Greeks.



Chem notes - section 4      posted 02-18-2008
Section 4
By the time of Demetri Mendelev in the 1880’s, then a young professor of chemistry in Russia, quite a lot about the various elements had been learned. Mendelev was the first to organize them into a pattern that recognized the repeating nature of the elements. That is, various elements – while unique – shared properties with other elements. For example, Sodium and Potassium reacted similarly with Fluorine or Chlorine. Mendelev placed these elements in rows and columns that reinforced their similarities. The rows were called “periods,” and the columns were groups or “families.” Sodium and Potassium were placed in the same family based upon their similar reaction with water. They made compounds long known to be alkaline, or basic. Further, they were observed to be metals so the family has been named the ”alkali metals.” The next column contains the similar elements Magnesium and Calcium. They also are metallic and produced alkaline substances. They were given the name “alkaline earth metals” in recognition of the ancient Greek concept of “earth,” the origin of many compounds containing calcium and magnesium.

Fluorine and Chlorine form salts with most metals, especially the alkali metals and alkaline earth metals. The Greek root for salt is “halo,” and the notion of formation is in the root “gen.” Therefore this family, which includes Bromine, Iodine and Astintine, is named “Halogen” for “salt-former.” Notably, the elements in this family are gaseous or solid at room temperature. They lack the malleability, sheen and electrical conductivity of metals and are therefore “nonmetals.”

At the time of Mendelev, the inert or “Noble Gas” family was not known. These are elements that usually do not enter into chemical reaction. The reason has to do with their atomic structure. They include Helium, Argon, Neon, Krypton, Xenon and Radon and are traditionally listed to the right of the Halogen family on the periodic table.

If you examine a modern periodic table, you will see the various groups and families. A zig-zag line on the right side of the table divides the semi-metals or “metalloids” and the non metals from the metals. Isn’t it amazing that so many of the elements are metals? Beside the groups mentioned above, we have the “transition metals,” including gold, iron, zinc and manganese as examples. We also have the “lanthanide” series and “actinide series.” The elements in these series follow Lanthanum and Actinium respectively. They are usually listed in two rows below the main table and their position indicated by lines.



Chem notes - section 5      posted 02-18-2008
Section 5
When you examine the periodic table, you observe that the atomic mass is not a whole number. Chromium, for example, has a mass listed on the periodic table in your text of 51.9961. Even Carbon, the basis of the table, has a mass of 12.0107, not 12.0000. How can this be? It is so if some atoms of the element have more or fewer neutrons than the vast majority of the atoms for that element. When the weight of the element is determined, the mass of the individual atoms is totaled and divided by the number of atoms. This gives the average mass. Practically, it is done by percentages. For example there are four known forms or “isotopes” of chromium. These are 50Cr, 52Cr, 53Cr and 54Cr. There is one form, 51Cr, that has been made in the laboratory, but it has such a short life that we do not consider it here. It is not believed to occur naturally. The atomic number of Chromium is 24, which means it has 24 protons and there are 26, 28, 29 and 30 neutrons respectively in the naturally occurring isotopes. Analysis of samples of Chromium show that there is 4.345% of 50Cr, 83.675% of 52Cr, 9.501% of 53Cr and 2.365% of 54Cr. We can find the average weight by converting percentages of each to the decimal form, multiplying by the mass of each isotope and adding the result together:

(0.04345)(50) + (0.83675)(52) + (0.09501)(53) + (0.02365)(54) = 51.9961

This shows you that the atomic mass listed on the periodic table is an “average.”

The metalloids, by the way, exhibit some properties of metals. For example, they are somewhat electrically conductive and find use in – of course – semiconductors in the electronic industry. In fact, transistors and modern computers as we know them would be impossible with out these elements.

As you examine the modern periodic table, you will probably marvel at its organization. For example, patterns and trends are there for all to see. Beside the periodic nature of the table and the way the atomic mass increases, the reactivity in terms of electronegativity becomes apparent as does atomic radius and ionic radius. For example, the atomic radius increases as you go down a column, or family. This is intuitive since additional electron orbitals are a characteristic of each, subsequent period of the table, and those orbitals increase the radius. Less obvious is how the atomic radius decreases as you move left to right across a period. This is a result of the increasing number of protons in the nucleus attracting and holding more tightly the electrons in the orbitals. The ionic radius – that is, the radius when an electron has been gained or lost – is not quite as intuitive. While it makes sense for the ionic radius of metals to decrease because protons are added left to right, but not additional layers of electrons, what about for the non metals? The radius of these ions – anions – also tends to decrease because of the increasing protons in the nucleus. This appears to be true even though electrons are added to the outermost shell.



Chem notes - section 6      posted 02-18-2008
Section 6
Because of the tendency of the elements to react – their electronegativity – Linus Pauling made a scale to show this. Fluorine, the most electronegative element was assigned the value of 4 on his scale. All other elements were rated based on it. Francium, in the lower left hand corner of the table, is least electronegative (0.7 on the Pauling scale). All elements have electronegativity between these two limits.

Previously, I wrote that the ideas of the Greeks drove early chemists down a dead-end path. I also wrote that they still found much along that path which was useful to later generations of investigators. These pioneers learned that some substances were denser than others; that is, equal volumes contained greater mass than others. Comparing their density was one way that counterfeit gold coins could be detected. They learned that “like dissolves like,” such as when salt dissolves in water but not in oil. They also found that different substances had different melting and boiling temperatures. Why would this be so? Clearly, it is a function of some property of the atom or – where atoms have joined together – of molecules, but what? Thinking about it, we realize that different amounts of energy – as heat – are needed to melt or boil the substance. The difference must reflect the amount of energy between the atoms or molecules holding them together: the stronger the interatomic or intermolecular forces, the higher the melting or boiling point.

Dalton’s realization that the same weight of one element might react with different weights of two other elements was the forerunner of the “mole concept.” This term, from the Latin term for “mass, massive structure,” is used to describe the number of combining units of a substance available for a reaction. It is based on the amount of the substance, typically in grams, and the atomic mass, referenced to carbon-12. Therefore it is a “made-up” definition, much as one dozen means 12 of something, like “a dozen eggs.” What might make for some confusion to the student is the fact that beside showing the relation between a mass and an atomic mass, the mole also is defined in terms of Avogadro’s number, 6.02 x 1023.

Let’s explore these concepts in a little more depth. First, understand that our system of measurement is based on the arbitrary assignment to Hydrogen of a mass of “1 atomic mass units” or “amu.” That is, it has a single proton to which a mass of 1 has been assigned. If there are intelligent beings elsewhere in the universe, they may have assigned hydrogen a different mass. However, regardless of the absolute mass, it would be so anywhere in the universe that what we named “carbon-12” has 6 protons and 6 neutrons. The mass ratio of carbon-12 to hydrogen will always be 12:1, regardless of the mass assigned by any of the “locals.” Notice that I am not including any isotopes – about which we will speak soon – of either hydrogen or carbon in this discussion. In this system, if we take one gram of hydrogen and divide by the atomic mass of hydrogen – 1 amu – our answer is 1 mole. If we have 12 grams of carbon-12 and we divide by the atomic mass of carbon-12 – 12 amu – we have 1 mole. The same is true for any element from Helium to Lawrencium.



Chem notes - section 7      posted 02-18-2008
Section 7
Now here is the interesting part: In one mole of Hydrogen, there are 6.02 x 1023 atoms of Hydrogen. In 1 mole of Carbon-12 there are – you guessed it -- 6.02 x 1023 atoms of carbon-12. So the mole is a short-hand way of taking the mass of the substance out of the equation and just considering the way atoms interact with each other based on their number. Let’s look at it as a mathematical expression:

6.02 x 1023 atoms = 1 mole = mass (grams) / atomic mass (amu)

Here is an example: You have 24.000 grams of carbon-12. The atomic weight of carbon-12 is defined as 12.000 amu. Dividing 24.000 by 12.000 is 2. Therefore, there are 2 moles of carbon-12 in 24.000 grams of carbon-12. Further, since 1 mole contains 6.02 x 1023 atoms of carbon-12, there are 1.20 x 1024 atoms of carbon-12 present in 2 moles.

When John Dalton noted that atoms could combine with each other to form various compounds, he could not have known that combining required interaction of electrons. It took work by early 20th century investigators such as J.J. Thompson, Gilbert Lewis and Irving Langmuir, to name just a few, to understand that there were several ways in which atoms could bond to each other, all involving what are called “valence electrons.” These are the electrons in the outermost orbital of an atom. With elements that have very few electrons in their outermost orbital, it is most easy for them to be “donated” to elements whose atoms need but few electrons to fill their outer orbital. Thus, even if the individual atoms then contain more or fewer protons than are balanced by the remaining number of electrons, the atoms are “stable.” That is, the electron shells that remain are complete. Atoms in this condition are called “ions.” They are named “Cations” and are positive when they have lost electrons and so have more protons than electrons. They are named “Anions” and are negative when they have gained electrons so there are fewer protons than electrons. Of course, the atoms are always found in a compound of two or more elements, so the charge on one is balanced by the opposite charge on another atom. For example, you cannot reach into a bowl of salt water and pluck out an individual sodium ion, leaving behind an unmated chloride ion.

The term “electronegativity” is used to describe the tendency of atoms of elements with different numbers of valence electrons to react with each other. Atoms of elements with one valence electron, for example, are highly reactive with atoms of elements that just need one electron to complete their outer shell. This is why alkali metals and halogens are so reactive; one wants to donate its electron and the other wants to accept it. Bonds formed in this manner are termed “ionic.” Compounds which display ionic bonding are always composed of a metal and non metal. They conduct electricity in solution, and form crystalline structures, not discrete molecules.



Chem notes - section 8      posted 02-18-2008
Section 8
Another class of bonding is termed “covalent.” This type of bonding involves atoms of similar or identical electronegativities. Rather than donate and receive electrons between atoms, the valence electrons are shared between atoms. This is sort of like a child who spends some of the time with one parent and the rest of the time with the other. Each parent can claim the child as their own, just as each atom can claim it has a full outer shell of electrons --- at least part of the time. Examples of covalent bonding include atoms of halogens reacting with each other to form molecules such as F2 or Cl2 (Fluorine gas and Chlorine gas, respectively). As you can see, there is a total difference between an element in its “atomic” form (Cl) and its “molecular” form (Cl2).

The third major type of bonding is called “metallic.” In metallic bonding, electrons are delocalized; they “belong to all” of the atoms in a sample of the substance. Not surprisingly, metallic bonding give metals their properties of heat and electrical conductivity.

Regardless of the type of bonding, it is often useful to look at HOW the atoms are bonded together. This gives an idea of the reactivity of the compound – or of the atom. Gilbert Lewis devised a method called “dot-diagrams” specifically to help chemistry students visualize bonding arrangements. The diagrams used the elements letter symbols with dots around them to show bonding to neighboring atoms and the number of bonds. For example, elemental carbon has four valence electrons; hydrogen has but one. To complete its outer orbital, could carbon donate its four electrons to hydrogen, or gain another four from four hydrogen atoms? This does not happen because the electronegativities of both elements are similar so the atoms share electrons. The dot diagram shows this:
H
..
H: C : H
,,
H

In this diagram, the hydrogen atoms have two electrons; one each of their own and one that they share with carbon. And the carbon has eight electrons which completes its outer shell, four of which were its own and the other four shared with the four Hydrogen atoms. This diagram also illustrates the “octet rule” which states that (most) atoms need 8 electrons to fill their outer shell and be stable. The formula for this compound – methane – is CH4 by the way.


MORE LATER



Question from Sheena, period 1 Biology, and reply      posted 02-11-2008
hi MR.STERN.! it's me sheena. i just want to ask your email address and about the homework today. 02/11/07. are we going to read page r8-r10 and r6-r7? because i realy get confused. BTW, im sorry if i sent an email from this e-add because i forgot what is your e-add. tc always MR.STERN. thanks

No problem. You are doing EXACTLY the right thing. My own email address is abinc@aol.com, but it is best for you to write to me at classbuilder.com because it keeps everything organized.

I want you to UNDERSTAND the pages; not copy them or summarize them. This is material you need to know. Pages R8 and R9 is a brief description of the microscope. Since I want you to learn to use the 'scope, the description on these pages is an O.K. way to become familiar with it. On page R10, it explains how to determine the size of a very small object by the magnification factors and a ruler. You need to understand that symbol that looks like a "u" is the Greek letter "mu." when you see "um," it is read "micron" and stands for 1 millionth (1/1,000,000) of a meter. When you see "mm," that means "milimeter" and is 1 thousandth (1/1,000) of a meter.

Pages R6-R7 describe how to make meaurements. The letter "g" stands for "grams."

I hope this answers your questions. Keep in touch if ANYTHING is unclear.

-- Mr. Stern

The Elements of Science Education Reform      posted 02-11-2008
Students, the following editorial by Gerald F. Wheeler, Executive Director of the National Science Teachers Association, mirrors my thoughts on science education. Please read the editorial and let your parents read it. Education today is too important NOT to have full participation by all people involved. That means you, the student; me, the educatior; the administrators and -- very, very important -- your parents. One thing you can do after you have read the editorial is to send me your thoughts on how I can best teach you the science that you need to compete in this world.

-- Mr. Stern

The Elements of Science Education Reform

2/1/2008 - NSTA Reports--Gerald F. Wheeler, Executive Director, NSTA
Our nation’s student achievement in science is, in a word, unacceptable. While corporate leaders, politicians, and educators have made a collective investment in reform efforts over the last three decades, we have still not seen real increases in our students’ understanding of science.
What must be done differently to achieve successful reform in science education? I believe we must meet four crucial challenges: (1) increase the science content knowledge of all science teachers, (2) develop a shared understanding of and focus on the most important ideas and skills students should learn, (3) raise parents’ awareness of the real needs our children will face, and (4) address these problems at a scale that impacts our whole education system.
Teachers need to know the science they have to teach.
Teacher preparation programs often fail to provide teachers adequate science content knowledge. Significant numbers of science teachers in the classroom lack degrees or even college coursework in science, especially at the elementary level. And with shifts in teaching assignments, teachers with a background in one discipline may be forced to teach another. The bottom line is too many of our nation’s science teachers don’t have a deep enough understanding of the science they teach. Several studies have suggested that as teachers’ understanding of science increases, so does student achievement. Research aside, it makes sense that teachers need to understand the science they teach.
We need a national focus on the most important ideas and skills.
We’ve got, arguably, good standards in the National Science Education Standards and Benchmarks for Science Literacy. But while Standards and Benchmarks have focused on conceptual understanding of a set of important ideas, they simply cover too much.
And the state-based standards developed in their wake only got bigger! Consequently, science teachers have far too many concepts to address, resulting in important ideas not getting the treatment they deserve, and students left with a poorly understood collection of facts and algorithms, quickly forgotten. Further complicating the problem, each state has different standards. A next generation of standards providing a national focus on the most important ideas is needed.
Of course, national consensus is difficult. However, a recent survey conducted by NSTA revealed strong support for a nationally shared focus. The survey asked science educators if a uniform set of national science content standards that every state would be required to use would be a good idea. Seventy-one percent agreed. This next generation of standards could respect the rights of states and local communities by centering on the ideas and skills that all states have declared important.
Parents need to be aware of their children’s real needs.
Today’s young adults are going to experience a world very different from their parents. Science and technology will have an increasing impact on politics, the economy, and on our personal lives. The politicians get it, business leaders get it, and, of course, educators get it. The challenge is that parents don’t get it.
A recent report by the Public Agenda shows that parents in a two-state survey, although aware of the importance of math, science, and technology for the future, remain complacent about the need for more rigorous courses. Seventy percent report “things are fine as they are.” (See the November 2007 issue of NSTA Reports, page 29, for a related article.) There’s no reason to believe that these survey results would be different in a national survey.
In order for reform to succeed—for student achievement in science to increase—we need a culture shift. Politicians, business leaders, and educators must find a way to energize parents and make them see the immediate importance of reform.
We need to impact a nation, not a classroom.
The final challenge is to address the scale of the problem: addressing the real needs of nearly two million teachers of science. To meet the scale of the problem, we need innovative programs that can act both nationally and locally.
At any single school site, many different content needs exist among a small number of teachers. But at a regional or national scale, we can move c

BASIC ASSESSMENT      posted 02-06-2008
PLEASE ANSWER THE QUESTIONS PRINTED BELOW. YOU MAY HAND THEM IN ON LINE OR IN CLASS. THIS IS A BASIC SKILLS ASSESSMENT.

1. What is 5/8 of 16/30?


2. Divide 27/32 by 3/8.


3. The concentration of a chemical in a mixture is 0.023%. How much of the chemical is in 78 grams?


4. 3/8 of a pound of iron is added to 2/3 of a pound of carbon. What is the total weight?



5. 3/26 of an ounce of magnesium oxide is taken from 29/13 ounces of it. How much is left?


6. How many feet in a yard?


7. How many inches in a yard?


8. How many centimeters in an inch?


9. How many centimeters in a yard?


10. 200 milligrams of a substance is added to 2.79 grams of the same substance. What percentage has been added?


11. A mixture is analyzed. It contains 4.5 grams of “A,” 17.06 grams of “B,” 0.06 grams of “C” and the balance is “D.” The overall weight is 30.19 grams. How much “D” is present? What is the percentage each of A, B, C and D in the mixture?




12. Express 0.0011 in scientific notation.



13. What is “standard format?” Give an example.



14. Express 3,259,609 in scientific notation.



15. How many significant figures in:
a. 3.104?

b. 1.0400?

c. 4000?

d. 0.0023

e. 1.9 x 10-3

16. The formula for a certain chemical compound is HxSyOz where "x, y and z" are subscripts that tell how many of a particular atom is present. For example, H2O -- water contains two atoms of hydrogen and one atom of oxygen for a total of three atoms in the molecule. Now, for the problem, if z = 4, x = 1/2 z and y = 1/2 x, how many atoms are present?

17. Carbon-14 is a radioactive isotope of carbon that decays to nitrogen at a predictable rate. The decay rate is used as a "clock" to determine the date of archelogical specimens. The "half-life" is the time it takes for one half of the radioactive carbon in a sample to decay. The half life for carbon-14 is 5730 years. In other words, if you have 10 grams of carbon-14 to begin with, then after one half life, you have 5 grams left.

a. Make sure you understand the question. Explain to yourself what "half-life" means.

b. How many half lives will have passed if the sample has 2.5 grams of carbon-14 left?

c. How many years will have passed in two half-lives for carbon-14?

18. The atomic weight of methane gas (CH4) is 16. The atomic weight of air is about 29. This means that methane gas is less dense than air so it will rise. We can demonstrate this by blowing a soap bubble with gas. As it rises, we can touch a flame to the bubble and watch it ignite. It's really fun to watch. But here is my question: if the bubble is 4 inches in diameter, how much gas is in it? (In other words, what is the volume of a sphere whose diameter is 4 inches? The formula is V = (4/3) x Pi (the value is 3.14, if you have forgotten) x radius cubed.

19. In biology and chemistry we often use equations of the form A = B divided by C. (A=B/C). If you know any two of these variables, you can solve for the third. For example, the volume (V) of a solid is 5.75 cubic inches and its mass (m) is 11.50 lbs. What is the density? (D = m / V)

20. This is the last question and it contains a trick. Think carefully before you answer.

a. What is the order of the numbers 1, 3, 5, 7, 9 ?

b. What is the order of the numbers 2, 4, 8, 16, 32, 64 ?

c. What is the order of the numbers eight, five, four, nine, one, seven, six, three, two, zero?





Biology, Chemistry, ICS and Environmental Science      posted 02-02-2008
Hello, Students. This note is to acquaint you with what we will be doing in your science class this 'mester. For those of you who have already provided me with your email address, you are probably reading this note online. For anyone else, you must get an email address and give it to me immediately. If you do not have a computer with internet access at home, you can use the computers here at school, at public libraries or at internet cafes. There is no excuse for not getting an email address.

This is the first spring 2008 'mester. As you know, 'mesters are approximately 10 weeks long. The class periods are 85 minutes in length giving us about 71 class hours to cover the material specified in the state standards for your subject. About three of those hours are taken by roll-call, even with assigned seating. You can expect two assessment tests, each of which take a class period, for another 2.6 hours. Class room interruptions and distractions steal more minutes which add up into hours. Realistially, we can expect no more than about 64 hours of good, solid class time to cover the material. Think about it! We lose about a week of educational time before we even get started! For that reason, I deal very strictly with students who do not come to order, who hold side conversations and who disrupt the class. It's nothing personal, you understand: we just won't put up with those who steal time from their classmates.

The students who are here to learn will be rewarded for their efforts. You will receive a copy of the class rules and an acknowledgement that you have received them. Those who follow the rules will at least pass the class. We will also have semester projects. These are likely to be hands-on activities conducted in as well as out of the classroom. Plan on participating in a group assignment. These are intended to teach you to work with others, to access resources, to present your results to an audience and to finish a job on schedule. Quizzes are planned on a weekly basis. In addition, prepare to "think." Expect "thought questions" on the board when you enter the room. While I am taking the roll, you will be expected to think about the questions, usually, with a classmate. Then, you will write up your thoughts on the subject (individually! Not with your classmate!) and submit them for grading.

Buy a lab notebook right away. No excuses. The notebook is for recording information like notes and experiments. I will collect the lab book from time to time and put a grade on it. I will cover the format for the lab book in the first week. I will supply paper for quizzes, thought questions and similar assignments unless I tell you otherwise.

When books are issued, write your name in them where indicated and get them covered. The textbooks in science classes cost about $100 each. If they are lost or damaged, this is the amount you will have to pay to the school. You will need to bring your book to class each day and take it home for reading or homework. Leaving it in your locker, or at home, is not acceptable.

We use a token/reward system in class. You will be issued two tokens to begin with. These can be used to request bathroom or water breaks ("comfort breaks"), for personal use of the class computer(s), or to play with the games I have for you in this room. Currently we have air hocky, pinball and "the Claw." Perhaps we will have more. You earn more tokens by good behavior, turning in complete assignments and high grades. You lose tokens by disrupting class, failure to clean up after yourself and similar reasons. You can play the games during lunch, sometimes after school and when we have "free-time." We have free-time when all students have completed the day's work and we have a few minutes left over at the end of class.

In the first few class hours, I will be doing the following for all classes:
- learning about you
- teaching you study skills
- showing you how to prepare and keep a lab notebook
- teaching you to write a laboratory report
- teaching you how to take notes
- assessing your background knowledge
- describing semester project possibilities, garden work related to your class, science fair
- helping you learn about persistence and determination

Thereafter, each class will follow an individualized curriculum. It will be provided in class or on line.

Any questions, please drop me a note online or see me during the lunch break. Let's not discuss individual problems during class.

Best wishes for a productive 'mester.

-- Mr. Stern








Environmental Science Classes -- Existing Energy Sources      posted 11-14-2007
Period 1 Students identified the following, existing energy sources (in order of historical use):
1. Wood (Francisco)
2. Solar (Jose Reyes)
3. Wind (Albert)
4. Gas (Mirna)
5. Coal (Angelena)
6. Hydro (David Lara)
7. Petroleum (Justin Williams)
8. Hydroelectric (Jed Miranda)
9. Nuclear (Bruce)
10. Electricity (Brandon)

Period 2
1. Manpower (Dakota)
2. Wood (Karla)
3. Wind (Daisy)
4. Water (Dakota)
5. Coal (Tania)
6. Petroleum (Mr. Stern)
7. Gas (James)
8. Geothermal (Carlos Pazlan)
9. Nuclear (Tania)
10. Solar (Carlos Pazlan)

All students: Do Internet or encyclopedia search for "Edwin Drake." Who was he? What did he do?

All students: Select one of the energy sources listed for YOUR PERIOD. Research it via Internet or encyclopedia. Write about it. Include the following four items as a MINIMUM (If you want more than a passing grade, you will include additional points.)
-Discovery
-Use
-Pollution Impact
-Cost

This assignment is due TOMORROW, Thursday (15 November 2007)

-- Mr. Stern





For chemistry students      posted 10-29-2007
Just to remind you, due tomorrow is the following: "Write a paragraph (or more) on how the magnet self-assembly demonstration relates to atomic bonding and self-assembly of molecules from atoms. Use text for reference."

In addition, copy and paste the address of the web site listed below into your browser. Go to the site. Read and study the section on the floating magnets. Use that as a reference.

voh.chem.ucla.edu/classes/Self-assembly/pdf/Self-Assembly Student Manual-v2.doc

-- Mr. Stern

Calculating wet and dry weights      posted 10-28-2007
This is for the Environmental Science classes:

The weight of an empty container is the TARE WEIGHT. The weight of the container WITH a sample is the GROSS WEIGHT. By subtracting the tare weight from the gross weight, you have the weight of the sample itself. This is the NET WEIGHT. When you begin an experiment, you have a STARTING or INITIAL WEIGHT. At the end of the experiment, you have a FINAL WEIGHT. When you express a fraction gained or lost in terms of the whole sample, you calculate a PERCENTAGE. For problem 3 on the quiz given 12 October, you had the following situation:

"The tare weight of a watch glass is 3.025 grams. The gross weight (wet) of a soil sample is 9.034 grams. After drying the gross weight (dry) is 7.084 grams."

A. What is the weight of the water in the sample?

All you have to do is subtract the dry gross weight from the wet gross weight. You don't have to account for the weight of the watch glass since it has not changed in weight. So subtracting 9.034 - 7.084 = 1.95 grams of water.

B. What is the dry weight of the soil in the sample?

Subtract the tare weight from the dry gross weight. That is 7.084 grams - 3.025 grams = 4.059 grams

C. What is the percentage water in the sample?

You want to know how much water was in the dry soil, as a percentage. Divide the amount of water by the amount of soil and multiply by 100. Thus (1.95 / 4.059) x 100 = 48 %.

ICS Class -- Electronics; the transistor      posted 10-24-2007
We will shortly be studying how the transistor works. Please go to the following web site and study the article on the history of this remarkable device.

http://www.pbs.org/transistor/teach/teacherguide_html/lesson1.html

-- Mr. Stern



Dynamic Earth Processes      posted 09-28-2007
STANDARD SET 3. Dynamic Earth Processes The earth sciences use concepts, principles, and theories from the physical sciences and mathematics and often draw on facts and information from the biological sciences. To understand Earth’s magnetic field and magnetic patterns of the sea floor, students will need to recall, or in some cases learn, the basics of magnetism. To understand circulation in the atmosphere, hydrosphere, and lithosphere, students should know about convection, density and buoyancy, and the Coriolis effect. Earthquake epicenters are located by using geometry. To understand the formation of igneous and sedimentary minerals, students must master concepts related to crystallization and solution chemistry.
Because students in grades nine through twelve may take earth science before they study chemistry or physics, some background information from the physical sciences needs to be introduced in sufficient detail. From standards presented earlier, students should know about plate tectonics as a driving force that shapes Earth’s surface. They should know that evidence supporting plate tectonics includes the shape of the continents, the global distribution of fossils and rock types, and the location of earthquakes and volcanoes. They should also understand that plates float on a hot, though mostly solid, slowly convecting mantle. They should be familiar with basic characteristics of volcanoes and earthquakes and the resulting changes in features of Earth’s surface from volcanic and earthquake activity.
3. Plate tectonics operating over geologic time has changed the patterns of land, sea, and mountains on Earth’s surface. As the basis for understanding this concept:
a. Students know features of the ocean floor (magnetic patterns, age, and sea-floor topography) provide evidence of plate tectonics.
Much of the evidence for continental drift came from the seafloor rather than from the continents themselves. The longest topographic feature in the world is the midoceanic ridge system—a chain of volcanoes and rift valleys about 40,000 miles long that rings the planet like the seams of a giant baseball. A portion of this system is the Mid-Atlantic Ridge, which runs parallel to the coasts of Europe and Africa and of North and South America and is located halfway between them. The ridge system is made from the youngest rock on the ocean floor, and the floor gets progressively older, symmetrically, on both sides of the ridge. No portion of the ocean floor is more than about 200 million years old. Sediment is thin on and near the ridge. Sediment found away from the ridge thickens and contains progressively older fossils, a phenomenon that also occurs symmetrically.
Mapping the magnetic field anywhere across the ridge system produces a striking pattern of high and low fields in almost perfect symmetrical stripes. A brilliant piece of scientific detective work inferred that these “zebra stripes” arose because lava had erupted and cooled, locking into the rocks a residual magnetic field whose direction matched that of Earth’s field when cooling took place. The magnetic field near the rocks is the sum of the residual field and Earth’s present-day field. Near the lavas that cooled during times of normal polarity, the residual field points along Earth’s field; therefore, the total field is high. Near the lavas that cooled during times of reversed polarity, the residual field points counter to Earth’s field; there-fore, the total field is low.
The “stripes” provide strong support for the idea of seafloor spreading because the lava in these stripes can be dated independently and because regions of reversed polarity correspond with times of known geomagnetic field reversals. This theory states that new seafloor is created by volcanic eruptions at the midoceanic ridge and that this erupted material continuously spreads out convectively and opens and creates the ocean basin. At some continental margins deep ocean trenches mark the places where the oldest ocean floor sinks back into the mantle to complete the convective cycle. Continental drift and seafloor spreading form the modern theory of plate tectonics.

3. b. Students know the principal structures that form at the three different kinds of plate boundaries.
There are three different types of plate boundaries, classified according to their relative motions: divergent boundaries; convergent boundaries; and transform, or parallel slip, boundaries. Divergent boundaries occur where plates are spreading apart. Young divergence is characterized by thin or thinning crust and rift valleys; if divergence goes on long enough, midocean ridges eventually develop, such as the Mid-Atlantic Ridge and the East Pacific Rise.
Convergent boundaries occur where plates are moving toward each other. At a convergent boundary, material that is dense enough, such as oceanic crust, may sink back into the mantle and produce a deep ocean trench. This process is known as sub

Persistence and Determination      posted 09-28-2007
Nothing in the world can take the place of Persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan 'Press On' has solved and always will solve the problems of the human race.
Calvin Coolidge
30th president of US (1872 - 1933)

Documents by email and set up for soil testing      posted 09-27-2007
Dear students --

This service, "Classbuilder.com" has a number of good features that will help me help you. However, I am not able to attach photos, diagrams, etc., to the email I send you. This is a problem. To go around it, I will have a website shortly that you will be able to visit and download documents in the correct format. Until then, I will give you links in the email that I send you so you can go to source websites and download information, or study data, there.

For environmental science, for the solar cell experiment, go here:

http://voh.chem.ucla.edu/classes/Solar_cells/pdf/Student_Solar.pdf

Please study this site before you come to class so you will know how the solar cell works.

For the soil analysis, here is more information:

1. Purpose: to determine the amount of organic matter in the soil.
2. Materials: well mixed soil sample (from sampling ring) -- about 50 grams, hot plate, balance, evaporating dish (watch glass)
3. Procedure: Scoop out or scrape out about 200 grams of soil. Mix it well. Then take about 50 grams of this portion and weigh it accurately. Put it on the hot plate set at mid heat -- not HOT -- and note its location on the hot plate. There is room for about 9 dishes or watch glasses on the hot plate. That is why I said to note its location. When the sample is at constant weight, it is dry. Weigh it again and record this weight. Then transfer all or a weighed portion to a crucible. It is important to know exactly how much you have placed in the crucible! Then, heat it with a bunsen burner until all organic materials have burned off. This needs to be done in the fume hood. Let it cool and reweigh.
4. Data: record the weights at each step.

If you have time between the steps, you can work on the solar cell experiment.

-- Mr. Stern




EARTH SCIENCE NOTES -- CONTINUED      posted 09-26-2007
(CONTINUED FROM PREVIOUS ASSESSMENT NOTES. THERE MAY BE SOME OVERLAP OF INFORMATION!)


Begin with the model in its closed position. The two points marked A and B should be juxtaposed, and the gaps at the two spreading ridges should be closed tightly. Now open the model. Note how new plate is "created" at each spreading ridge and an equal area is added to each of plate A (the shaded plate) and plate B (unshaded). Also, notice that after spreading has occurred, the two ridges are no farther apart than before spreading. Verify this by measuring distance DD' with the model closed and distance EE' with the model open.
The model illustrates the fact that the shape of an


oceanic ridge does not change with time.
Now turn your attention to the fault itself. With the model closed, imagine yourself standing on point A, looking across the fault to the juxtaposed point A'. Slowly open the model, watching how point A' moves as seen from point A. If you are standing at point A, you will see point A' move to your right.
Turn the model upside down and repeat the process. If you are standing at point A', you will see point A moving to your right. Because of this independence of where you happen to stand, this particular transform fault is said to display right-lateral motion. That is, the motion is side-to-side and the other side of the fault always moves to your right.
Transform faults may also be left-lateral, if the ridges are offset in the opposite sense. To see this, turn the model page over to the other side and trace the positions of points A and A' on the reverse side of the paper. Holding the closed model so that you are looking at its reverse side, open it and note the motions of points A and A'. If you are standing at point A, you will see point A' move to your left.
The combination of ridge segments and transform faults forms a rectilinear zigzag pattern for oceanic plate boundaries that may be seen clearly in Figure 3-3. It is still not clear just how this zigzag pattern is formed initially, but because the pattern does not generally change shape with time, it must have come into existence at about the same time as the ridges themselves. The process by which this happens is still not fully understood.
Where transform faults cut across continents, however, they tend to be long and relatively continuous, with few, if any, spreading segments. The best known and most studied example of a continental transform fault is California's San Andreas.
Now look at the satellite photo shown below. It shows land and ocean floor to the west of the San Andreas Fault. This area is part of the Pacific Plate and is moving to the northwest, parallel to the fault. To the east of the fault is the North American Plate. Where the San Andreas Fault crosses the North American continent it is long and unbroken, but where it goes out to sea, it is cut into shorter segments separated by spreading ridges. Some of the ridge segments themselves are quite short, as in the Gulf of California.
Note that the ridge and fault geometry is similar to that of your paper model, for which right-lateral motion is expected along the fault. This is in fact
what is observed along the length of the San Andreas. It is a classic transform fault, where the Pacific Plate is sliding past the North American Plate, carrying Los Angeles and Baja California along with it.
Along the fault, the rocky edges of the plates grind against one another. In a few places, the slippage occurs smoothly. Here, any structure such as a fence or road that crosses the fault is offset at a rate of up to six centimeters (2-1/2 inches) per year. But in other places, the fault is jammed and does not move steadily. As the plates continue their inexorable motion, the forces exerted on the pinned fault build up with each passing year. Finally the rock can stand no more and it breaks, unleashing the pent-up energy as strong vibrations of the ground: an earthquake.











TECTONIC PLATE BOUNDARIES:
There are three mechanisms of plate movement and associated geological phenomena that are known. These are transforms faulting and movement, which you saw above, sea-floor spreading – also discussed previously – and subduction.
In subduction, one tectonic plate dives beneath another. It results in volcanic activity on the top plate miles in from the point where the plates actually met. Use the hyperlink to go to “Sea-floor spreading and subduction model.” This is a web site established by the USGS and it shows the phenomena clearly. You can also build a “shoe-box” model of it.


IGNEOUS ROCK CHRACTERISTICS

(This discussion is taken from the website “PhysicalGeography.net.” For more information, use the hyperlink to go to the site. )
First, only igneous rocks originate as molten magma. The type of igneous rocks that form from magma is a function of three factors: the chemical composition of the magma; temperature of solidification; and th

ICS 1 CLASS -- NOTES ABOUT EARTH SCIENCE      posted 09-26-2007
(NOTE: THE ILLUSTRATIONS THAT ARE SUPPOSED TO ACCOMPANY THIS TEXT ARE NOT BEING COPIED. I'LL FIGURE OUT ANOTHER WAY OF GETTING THE INFORMATION TO YOU. IN THE MEAN TIME, STUDY WHAT I HAVE WRITTEN (OR ABSTRACTED FROM OTHER SOURCES) TO PREPARE FOR YOUR FIRST ASSESSMENT TEST. IT WILL BE IN ABOUT A WEEK.) I WILL PROVIDE MORE INFORMATION IN CLASS.

-- MR. STERN

LANDSLIDES


As you examine this picture, you see landslides caused by a variety of natural actions. For example you can see how rocks can be weathered to form sediments which can tumble down. You can see how disturbances such as road construction can move sediments and cause landslides. Is it possible for movement of one tectonic plate under another to trigger landslides? If you said “yes,” you are correct. But can such movement – subduction – move sediments down the mountain slopes?


EARTHQUAKES AND MEASUREMENT

Earthquake Magnitude - Quantitative measure of the energy released by an earthquake at its source. Measured by the Richter Scale magnitude (each step = 31 times increase in energy = 10 times increase in earthquake wave amplitude). Magnitude 6 earthquake = Megaton nuclear bomb in damage potential. Largest recorded earthquake was magnitude 8.6 (1964 Alaska earthquake). Most earthquakes have a magnitude of < 2.5. The largest earthquakes (> 8.0 magnitude) occur on average every 5 years. Magnitude determined by:
1. Measurement of seismic wave size (amplitude).
2. Distance from epicenter - Magnitude decreases with distance from source.
3. Sensitivity of the seismograph.
THEORY OF PLATE TECTONICS
Although Plate Tectonics is a theory, there is evidence that supports it:

1. The shapes of many continents are such that they look like they are separated pieces of a jig-saw puzzle.
2. Many fossil comparisons along the edges of continents that look like they fit together suggest species similarities that would only make sense if the two continents were joined at some point in the past.
3. There is a large amount of seismic, volcanic, and geothermal activity along the conjectured plate boundaries. Remember the map titled “Dynamic Earth?”
4. There are ridges, such as the Mid-Atlantic Ridge where plates are separating. New ocean floor is produced by lava welling up from between the plates as they pull apart. Likewise, there are mountain ranges being formed – like the Himalayas -- where plates are pushing against each other.

If the crustal plates are pulling apart at boundaries like the Mid-Atlantic Ridge the sea floor near these ridges should be very young geologically, since it is formed of material upwelling from the interior. This is indeed the case, as the preceding figure shows. The estimated age of sea floor crustal plates in red is youngest and blue the oldest. The material near the crustal boundaries is clearly young geologically.













FAULTS: TRANSFORM FAULTS
Transform faults are long and relatively continuous where they cut across continents, but tend to appear as short discontinuous segments offsetting sections of spreading ridges on the ocean floor. The transform fault is simply a fault connecting two other kinds of active plate boundaries, but that is a deceptively simple definition. Look at the first figure, below. It is a model of a transform fault that you can print out, construct and study. Please do this now. Follow the directions. Your model is very similar to small portions of the Mid-Atlantic Ridge between South America and Africa.
For more information on paper models of transform faults, go to this website: http://web.mala.bc.ca/earle/transform-model/
Begin with the model in its closed position. The two points marked A and B should be juxtaposed, and the gaps at the two spreading ridges should be closed tightly. Now open the model. Note how new plate is "created" at each spreading ridge and an equal area is added to each of plate A (the shaded plate) and plate B (unshaded). Also, notice that after spreading has occurred, the two ridges are no farther apart than before spreading. Verify this by measuring distance DD' with the model closed and distance EE' with the model open.
The model illustrates the fact that the shape of an


oceanic ridge does not change with time.
Now turn your attention to the fault itself. With the model closed, imagine yourself standing on point A, looking across the fault to the juxtaposed point A'. Slowly open the model, watching how point A' moves as seen from point A. If you are standing at point A, you will see point A' move to your right.


(THESE NOTES ARE CONTINUED IN THE NEXT BLOG)

Welcome to the Fall 2007 'mester at Panorama HS      posted 09-03-2007
Chemistry and Environmental Science will be really exciting this year. I welcome you all. We have a service learning project, a horticultural project and opportunies for field trips. I have prepared a class syllabus and introduction to each class. They appear below and are subject to revision. Hard copies will be provided in class because the format changed when I copied the material to this Blog. As it is, you can make out the topics to be covered, but the schedule is hard to understand. It will be clear when you look at the hard copy.

One of the first things we will do is to take a series of assessment quizzes. These will help me understand and respond to your needs as students more quickly and efficiently.

To take the assessments you will need access to the Internet. If you don't have it at home, you will need to use computers at the school library or other source. If this is impossible then I will permit written assessments, but just on a case-by-case basis.

-- Jay L. Stern

For Chemistry:

CLASS SCHEDULE AND SYLLABUS, CHEMISTRY “A” – Fall 2007

Chemistry class meets five days per week, 85 minutes per meeting for ten weeks. That allows us 71 hours to cover the first half of the state-mandated curriculum. The remainder will be offered in Chemistry B, which will also be ten weeks long. We have enough time to cover the material adequately for you to understand and enjoy it -- hopefully. We do not have time for individuals who steal time from their classmates by disrupting the lesson.

Here is how the class will be conducted:

1. Materials and book: You will need a one-subject 8-1/2” x 11” spiral notebook for class notes and homework. You will need a quadrille-ruled lab book for experiments. The price for the spiral notebook is currently about $1.50 and for the quadrille-ruled lab book, $2.48 at Staples. NO OTHER STYLE NOTEBOOKS ARE TO BE USED IN THIS CLASS. You must bring the spiral notebook to class every day. The lab notebook stays in the classroom. You are also to have with you at least two dark blue or black pens. Written work in other colors will not be graded. If pencils are needed, especially colored pencils, they will be supplied and collected at the end of the lesson. You will be issued a text book. You must cover it and have it every day. You will be expected to turn it in at the end of the semester. We will also use supplemental reading material, worksheets and notes. HAVE NOTEBOOKS, PENS AND A BOOK COVER (TO FIT BOOK 9” X 10” X 1-1/2”) BY CLASS TOMORROW!

2. Class rituals and routines: Enter the room quietly before the bell rings. Pick up your lab book from its storage location. From time to time, you will have a worksheet, quiz, etc. to pick up as well. Generally, these will be in the same area as your lab book. Then take your ASSIGNED seat.

Write the current date on a fresh page of your lab book. On the board will be a research question, notes about the current experiment or project, or other writing assignment. Use your lab book as a JOURNAL and write about the topic on the board. You may be provided with more instruction as needed. While you are writing, roll will be taken.

You will have about ten minutes for writing. We will then discuss the topic for around another ten minutes. Usually, the topic will lead into a class assignment or lab. If it is a class assignment, you will take notes in your spiral notebook. If it is a lab, you will use your lab book. Directions will be given on how to (a) effectively take notes and (b) keep a lab notebook. Some class work and the labs will be completed in groups. Other work, like quizzes, will be individual effort

Homework assignments will be written on the board or issued on worksheets. It is your responsibility to copy each assignment into your spiral notebook. Expect to refer to or read sections of your textbook at home. When exercises are assigned, they will come from your textbook. Complete them on paper from the back of your spiral notebookor other paper, if you wish, so long as it is 8-1/2” x 11” in size. Points will be deducted from your grade if you violate this rule.

Class work will end about five minutes before the bell. You will have time to collect your belongings, put away your lab book and clean up your work area. BUT…THE BELL IS THE TEACHER’S SIGNAL TO DISMISS. YOU ARE TRUANT IF YOU LEAVE THE ROOM BEFORE DISMISSAL.

3. Comfort breaks: You will be issued slips for five, 10-minute comfort breaks during the semester. To leave the room for a comfort break, you will need to surrender one slip and take the school’s hall pass. Only one student at a time is permitted to leave the room on a comfort break. You should treat your comfort break slips like money and protect them. If you must exceed five breaks in the semester, expect to lose grade points. You may barter or sell unused slips to other students. At the end of the semester, you may turn in

Basic chem skills assessment given to students -- all did poorly      posted 02-06-2007
This is the assessment I gave the students to see how well they would understand the math used in chemistry. All students did very poorly. You may want to work with your child to assist them.
-Jay L. Stern

Name _____________________
Date _________ Per. # _______
Chemical Skill Questionnaire (Work on your own paper. Write answers here. Attach worksheet to this questionnaire.)


1. What is 5/8 of 16/30?


2. Divide 27/32 by 3/8.


3. The concentration of a chemical in a mixture is 0.023%. How much of the chemical is in 78 grams?


4. 3/8 of a pound of iron is added to 2/3 of a pound of carbon. What is the total weight?



5. 3/26 of an ounce of magnesium oxide is taken from 29/13 ounces of it. How much is left?


6. How many feet in a yard?


7. How many inches in a yard?


8. How many centimeters in an inch?


9. How many centimeters in a yard?


10. 200 milligrams of a substance is added to 2.79 grams of the same substance. What percentage has been added?


11. A mixture is analyzed. It contains 4.5 grams of “A,” 17.06 grams of “B,” 0.06 grams of “C” and the balance is “D.” The overall weight is 30.19 grams. How much “D” is present? What is the percentage each of A, B, C and D in the mixture?




12. Express 0.0011 in scientific notation.



13. What is “standard format?” Give an example.



14. Express 3,259,609 in scientific notation.



15. How many significant figures in:
a. 3.104?

b. 1.0400?

c. 4000?

d. 0.0023

e. 1.9 x 10-3