Wednesday, December 8

We started class today by doing page 1 in the unit packet.
The following statements are false:

• Gases are massless matter. Gases are made up of atoms, which have mass.
• Gases will condense when heated. Gases expand when heated.
• Gases are colorless. I2(g) is purple, NO2(g) is brown.
• Gases push on the walls of their container, but ONLY in a downwards direction due to the influence of gravity. Consider a balloon; gas is pushed in ALL directions on the wall
• The volume of a gas is inversely related to the temperature of a gas. They are directly related. As temperature increases, volume increases.
• The particles of a sample of gas are relatively motionless. The particles move very quickly.
• The entire column of our atmosphere applies pressure on objects on Earth; this pressure is so small that it is of little consequence and influence.

We then did page 2, #4. The units for pressure are atm, psi, mm Hg, torr, and Pa. The units for volume are L, m3, and mL. The units for temperature are celcius and Kelvin. The answers are:

a) P

b)V

c)V

d)P

e)P

f)T

g)V

h)P

i)P

j)T

We then did #5 on page 2. To do this, we had to use the equation °C+273=K

For a, we were given 100°C to convert to K. The answer was 373 K since 100+273=373.
For b, we were given 400 K to convert to °C. The answer was 127°C since 400-273=127.
For c, d, and e we had to use converting factors.
1 atm=14.7 psi=760 mm Hg
The answers were:
c) 1.03 atm
d) 3.0 atm
e) 684 mm Hg (torr)

We then did page 3, #8 and 9. To determine the pressure, you take the difference in height and add or subtract from 760 mm Hg. For the second manometer in #8 you had becuase P has more pressing power than Hg. For that one, P=700 mm Hg + 760 mm Hg = 1460 mm Hg. In the third one, the gas outside has more pressing power, so you subtract the difference in height. P=760 mm Hg - 560 mm Hg=200 mm Hg.

For #9 we did something similar to measure pressure. For A, we had to convert 75 cm (the differnence in heights) to 750 m Hg. For B, we subtracted the two heights, 82 cm- 25 cm, to get 57 cm which we then converted to 570 mm Hg. For C, we also subtracted the two heights, 125 cm-50 cm, to get 75 cm which we converted to 750 mm Hg.

We then wrote down the answers to the Chapter 5.2-3 reading sheet on page 27 about gas laws. The answers are:

1. a, b

2. b, c, d

3. a

4. b

5. d

6. c

7. a, ,b c, d

8. a

9. d

10. c

11. d

12. b, c, a

13. a

14. b, c

We ended class with some interesting demos. In one, Mr. H put a vlown up balloon in liquid nitrogen. That caused the volume to decrease because the the nitrogen is very cold, so the temperature had decreased. It was so cold that the air turned into liquid air. He also froze a water bottle by putting it in the liquid nitrogen. Another demo was to take the shrunken balloon and quickly put it in an empty bottle. As the temperature increases, the volume of the balloon increases causing there to be a blown up balloon inside a water bottle. At the very end of class, Mr. H poured the liquid nitrogen all over the floor where we watched it seem to disappear as it turned into a gas.

Monday, November 1

We started class today by turning in our homework from the Chemthink assignment. We reviewed what we learned on Friday about chemical reactions. Here are some facts about chemical reactions:

• Always rearrangement of atoms



• Breaks bonds and forms new bonds



• Reactants (starting materials) turned into products (ending materials)



• Conservation of mass (atoms are neither created nor destroyed)



• Conservation of charge (protons and electrons are neither created nor destroyed)



• Represented symbollically by chemical equations

We then practiced what we learned by doing page 1 in the unit packet.

Question 1 involved writing the formula of reactants and products based on a picture. We talked about turning the visual into words, so it would be 1 molecule of methane gas reacts with 2 molecules of oxygen to create 1 molecule of carbon dioxide and 2 molecules of water. We then were able to write the formula for that. The arrow between the reactants and products represent that the reactants turned into the product. In question 2, we had to use our unit 1 skills to count the number of atoms in different chemical reaction formulas. The numbers should be equal in both sides of the equation, which means that the atoms were conserved. For questions 3 and 4 we had to count the number of each atom on the reactant and product side of a given equation. If there are the same number of atoms on both sides, that means it is a balanced equation.

We then learned about balancing chemical equations. Here are some important things to remember while balancing a chemical equation.

• Add coefficients in front of formulas. (Do NOT change formulas' subscripts and supersubscripts)


• Trial and error process

- do one element at a time; pick the element that is present in one location on reactant and product side

- use whole number coefficients; if a coefficient comes out to be a half number, double them all

We practiced balancing equations by doing page 2 in the packet.

With question 5, we started with balancing N. Since there were 2 N molecules on left, but only 1 on the right, we added a coefficient of 2 in front of NH3 on the product side. That caused there to be 6 H molecules on the product side. We added the coefficient 3 in front of H2 so that there would also be 6 molecules of H on the reactant side. The balanced equation was now N2+3H2 ---> 2NH3. To make sure this is correct, you could count the number of each atom on each side and make sure they are equal. Mr. H reminded us to make sure that when balancing equations, you always want the lowest possible set of whole numbers.

We were assigned our homework, which is to read page 5-6 in the packet and 60-61 in the textbook. These are about classifying reactions.

We ended class with a demonstration of the solid zinc reacting with the aqueaous hydrochloric acid. This created hydrogen gas and zinc chloride. The chemcial formula for it looked like this:

Zn(s)+2HCl (aq) ---> H2 (g) + ZnCl2 (aq)

The signs that this was a chemical reaction were that a gas formed and the test tube was warm.

Here is a video of the reaction of zinc with hydorchloric acid.

http://www.youtube.com/watch?v=CfrsElKZaLU&feature=related

Monday, September 13

We started class today with Mr. Henderson telling us to get out our calculators, lab notebooks, packet, and to make sure we had patience. We began class by reviewing Lab MM6, the Conservation of Mass Lab. During this lab, we measured the mass of chemicals before and after a chemical reaction. The purpose was to figure out if mass was retained or changed during a chemical change. One person from each lab group went to the front of the room to record their data so we could see what the overall data of the entire class was. This is what the class data turned out be:

We then discussed whether or not the results of the lab shows that mass is retained during a chemical change. Some people said that mass was lost, since some of the masses decreased lightly. Others said that the mass stayed the same because it only changed slightly. Mr. Henderson told us that the mass had stayed the same. He said that in chemistry, 157.37=157.21. This could be because of the uncertainty or some of the chemicals may have fallen out when it was measured for the second time.

Once we finished reviewing the lab, we started to learn about metric conversions. We were told we had to memorize four of the prefixes. We learned a great way to remember them.

1 kilometer=1000 meter

100 centimeters= 1 meter

1000 millimeters=1 meter

10^9 (1,000,000,000) nanometers=1 meter

We also learned a way to remember the many different prefixes by using a scale.

We learened how to use this scale to do metric conversions. If you wanted to convert a kilometer to a meter, you move the decimal place 3 places to the right since the base unit is 3 spaces to the right of the kilo. If you wanted to convert millimeters to meters, you move the decimal place 3 places to the left since the base unit is 3 units to the left of the milli. We practiced doing this by doing a worksheet, page 7 in the packet.

We then went over problems 7 and 8 form the worksheet. 7 was converting 1 mL to kL. First we learned to convert it to L. If you move the decimal place 3 to the left, you get 0.001 L. If you move that 3 more places to the left, you get 0.000001 kL. for 8, the problem was to convert 1.0 Mg to mg. Mg was not on the scale, but it was listed on the worksheet as 10^6. If you calculate 1.0 X 10^6, you get 1,000,000 g. It still needs to be put into mg from g, so you move the decimal place 3 spaces to the right. The solution to that is 1,000,000,000 mg (10^9 mg).

We finished class by being assigned our homework to do a Webassign reading sheet for tomorrow and our Delicious Assignment, which is due on Friday. Overall, it was a very productive class.