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.