1. Launch: 2/23
 Grab your binder and immediately take a seat!
 Place launch paper and yesterday’s practice questions
on your desk.
 Yesterday’s Exit Slip Data:
94%!
 Today’s Objective: Exam Review!

2. Launch: 2/23
 Grab your binder and immediately take a seat!
 Place launch paper and yesterday’s practice questions
on your desk.
 Yesterday’s Exit Slip Data:
87%
 Today’s Objective: Exam Review!

3. Launch: 2/23
 Grab your binder and immediately take a seat!
 Place launch paper and yesterday’s practice questions
on your desk.
 Yesterday’s Exit Slip Data:
93%!
 Today’s Objective: Exam Review!

4. Launch: 2/23
 Grab your binder and immediately take a seat!
 Place launch paper and yesterday’s practice questions
on your desk.
 Yesterday’s Exit Slip Data:
N/A
 Today’s Objective: Exam Review!

5. Launch 2/23
1. What is the combined gas law?

6. Launch 2/23
3. Choose the right equation.
At a constant temperature, a sample of CO2
gas occupies a volume of 20mL at 2 atm.
What will the volume of the gas be if the
pressure is increased to 20 atm?
a.
P1 P2
= V T1× V1 = T2× V2
V1 2
b.
V1 V2
P1× V1 = P2× V2 = T
T1 2

7. Launch 2/23
3. The temperature of a gas at 80mmHg is
decreased from 100K to 50K at constant
volume. What is the new gas pressure?
a. 40 mmHg
b. 50 mmHg
c. 500 mmHg
d. 800 mmHg

8. Announcements
 Today is a really important day!
 50 points for A-level review notes
 50 points for A-level review worksheet
 Exam on Thursday!
 Jeopardy tomorrow?
 For extra help, come in:
 Before school (7:15am – 8:05am)
 At lunch

9. February Calendar
Quiz!
Today Exam!

10. Unit #7 Exam Review:
Gases
Mr. Heffner
2/22/10

11. What is kinetic molecular theory?
 Kinetic molecular theory states that…
 gas molecules move fast and randomly

12. What is diffusion?
 Diffusion is…
 the process by which gases mix
Gas B
Gas A
random
movement

13. Example #1
If gas molecules are fast, why is there a
delay in smelling vinegar across a room?

14. What is temperature?
 Temperature is… movement
 a measure of the kinetic energy in a substance
 °C and K
K = °C + 273

15. Example #2
Convert 37°C to Kelvin.
plug & chug
K = °C + 273
K = (37) + 273
K = 310
310 K

16. What is pressure?
 Pressure is…
 created by random collisions with a surface
 atm & mmHg
temperature = collisions = pressure
T & P are directly related

17. What is Absolute Zero & STP?
standard temperature
& pressure
Absolute Zero STP
 all motion stops!  standard for experiments
 Temp = 0K -273°C  Temp = 0°C 273K
 Pressure = 0 atm  Pressure = 1 atm 760mmHg

18. Example #3
Which of the following correctly show the
conditions at STP?
a. 0 atm and 0°C
b. -273°C and 1 atm
c. 0K and 760mmHg
d. 760mmHg and 273K

19. What is volume?
 Volume is…
 the space that an object takes up
 L & mL
temperature = volume
T & V are directly related

20. What is the combined gas law?
 The combined gas law is…
P1× V1 P2× V2
=
T1 T2
 There is a 3 step process for solving gas equations:
1. Write down the combined gas law
2. Circle given units and cross out the extras
3. Re-write the equation, plug-in, and solve!

21. Example #4
At constant volume, a gas at 100K and 8 atm is cooled to
25K. What is the new gas pressure?
 Step 1: Write down the combined gas law
P1× V1 P2× V2
=
T1 T2

22. Example #4
At constant volume, a gas at 100K and 8 atm is cooled to
25K. What is the new gas pressure?
 Step 2: Circle the given units and cross out the extras
P1× V1 P2× V2
=
T1 T2

23. Example #4
At constant volume, a gas at 100K and 8 atm is cooled to
25K. What is the new gas pressure?
 Step 3: Re-write the equation, plug-in, and solve!.
cross-
P1
8atm P2 multiply
= T
✕ 25K
T1
100K 2
(P2)(100K) = (8 atm)(25K)
100K 100K
P2 = 2 atm

24. Practice Questions
 Review worksheet

25. Closing
 Study Hard!
 Unit #7 Exam in 2 days!

26. Exit Slip
1. How do gas molecules move?
a. in a random pattern, colliding with other gas
molecules as they move around
b. they move in a straight line
c. they always move from areas of low concentration to
high concentration
d. like ions found in a crystal lattice of NaCl

27. Exit Slip
2. Water boils at 373K. What is that
temperature in Celsius?
a. -100K
b. 100K
c. 173K
d. 646K

28. Exit Slip
3. Would you expect a gas at 100°C to have a
higher pressure than a gas at 0°C?
a. No, because it has less kinetic energy
b. No, because it has a higher temperature
c. Yes, because it has more random collisions
d. Yes, because it has less kinetic energy

29. Exit Slip
4. How are P & V related?
a. They are directly related.
b. An increase in volume increases pressure.
c. They change in the opposite direction
d. They are indirectly related

30. Exit Slip
4. The volume of 400mL of Ne gas at
100mmHg is decreased to 200mL at
constant temperature. What is the new gas
pressure?
a. .5 mmHg
b. 200 mmHg
c. 200 mL
d. 2000 mmHg

31. Homework
 Finish practice questions