1. Intro to Gases

2. Kinetic Molecular Theory of Gases
Attempts to explain the behavior of an ideal gas.
Gases consist of tiny particles.
Particles are so small, volume (size) of individual particles are assumed to be zero.
Particles are in constant random motion, colliding with walls of container  gas exerts pressure.
Particles are assumed not to attract or repel each other

3. Kinetic Molecular Theory of Gases cont
5. Average kinetic energy of gas particle is directly proportional to Kelvin temperature of the gas.

4. How Temperature affects K.E. of a gas
higher
faster
The _________ the temperature the __________ the particles move, so the _________ K.E. the particles have! (________ Relationship: As Temperature increases, K.E. increases.)
At 0˚K, (______________
______),
kinetic energy is also ________.
Direct
more
absolute
zero
zero

5. If particles are not moving, what must be the temperature? Temperature
Temperature is the average kinetic energy of a molecule.
If particles are
not moving, what
must be the
temperature?

6. Gas Particles & Pressure
increase
As the # of gas particles ____________, the pressure of a rigid container will ____________ if the temperature and volume of the container remain constant.
increase
# particles ___, P ___ ↑ ↑

7. Pressure Units for Pressure:
All gases exert pressure
Exerts pressure on its surroundings
A Barometer – a device that measures atmospheric pressure
SI Unit for Pressure: pascal (abbreviated Pa)
Units for Pressure:
1.0 atm = 101,325 Pa = kPa = 760 mm Hg = 760 torr = psi (lb/in2)

8. Gas Particles & Pressure

9. Boyle’s Law V___, P ___ decreases increase ↓ ↑
At a constant temperature, as the volume of a container __________ the pressure of the container will ___________.
V___, P ___
decreases
increase ↓ ↑
Pressure
Volume

10. Gases Particles & Volume
What happens when we blow air into a balloon?
As the # of gas particles _____________, the volume of a flexible container will ____________ (if the temperature and pressure of the container remain constant)
increase
increase
# particles ___, V ___ ↑ ↑

11. Charles’ Law T___, V ___ increases increase ↑ ↑
At a constant pressure, as the temperature of a container __________ the volume of the container will ___________.
T___, V ___
increases
increase ↑ ↑
Volume
Temperature (K)

12. Gay-Lussac’s Law increases increase ↑ ↑ T___, P ___
At a constant volume, as the temperature of a container __________ the pressure of the container will ___________.
increases
increase ↑ ↑
T___, P ___
The ABC’s of Gas Video!
*Heating a rigid container causes the gas inside to move faster which causes more pressure.
Too much heat will make it explode!
Pressure
Temperature (K)

13. Exit Slip (turn me in tomorrow!)
1. If you increase the temperature, what happens to the speed of gas particles? 2. Explain what would happen to the size of a balloon on a hot day.

14. Gas Laws

15. KELVIN I am LORD KELVIN K = ˚C + 273 ˚C = K - 273 Temperature Unit
When doing calculations, we want our temperature in:
KELVIN
K = ˚C + 273
˚C = K - 273
I am LORD KELVIN

16. Standard Temperature and Pressure (STP)
Often the volume of a gas is needed at “standard conditions.” For scientists, this means “STP”. Standard temperature is ______K, and standard pressure is equal to ___ atmosphere (atm)
273 1

17. Charles’ Law T___, V ___ increases increase ↑ ↑
At a constant pressure, as the temperature of a container __________ the volume of the container will ___________.
T___, V ___
increases
increase ↑ ↑
Volume
Temperature (K)

18. Charles Law Example
A sample of gas at 15 ˚C (at 1 atm) has a volume of 2.58 L. The temperature is then raised to 38 ˚C (at 1 atm). (1) Does the volume of gas increase or decrease? (2) Calculate the new volume

19. Gay-Lussac’s Law increases increase ↑ ↑ T___, P ___
At a constant volume, as the temperature of a container __________ the pressure of the container will ___________.
increases
increase ↑ ↑
T___, P ___

20. P1V1 = P2V2 Boyle’s Law V___, P ___ decreases increase ↓ ↑
At a constant temperature, as the volume of a container __________ the pressure of the container will ___________.
V___, P ___
P1V1 = P2V2
decreases
increase ↓ ↑
Pressure
Volume

21. Argon gas has a pressure of 2 atm at 35 ˚C (at constant volume), but the temperature was decreased to 20 ˚C . What is the new pressure?
An unknown gas at 240K (at 1 atm) has a volume of 1.5 L. The temperature is then raised to 300 K (at 1 atm). What is the volume of the new gas?
A 2.0 L sample of a gaseous compound is at a pressure of 1.0 atm. If the volume is changed to 0.75 L at a constant temperature, what is the new pressure?

22. (initial conditions) = (final conditions)
Combined Gas Law
Combines all the previous three laws.
P1 V1
P2 V2 = T1 T2
(initial conditions) = (final conditions)
Using the Combined Gas Law requires you to have the temperature in _____________ units.
The pressure and volume units can be anything as long as the initial and final units are ______ __________.
Kelvin
the same

23. Exit Slip (turn me in today!)
A sample of a gaseous compound has a pressure of 240 torr at 40˚C (at constant volume), but the temperature was decreased to 28 ˚C . What is the new pressure?

24. Gas Law Practice acc
Side 1: 1) a. V b. P c. T d. T e. V f. P 2) Speed Up! Increase 3) Decreases, Boyle’s 4) Decreases, Gay-Lusaac 5) 16 L 6) Increases, 2100 mm Hg 7) Increase, 4 atm 8) 8.0 atm 9) 10) Box 1 11) a psi b kPa c. 300,074 Pa Side 2: 1) K 2) 1.41 atm, G-L 3) 569 mL, Charles 4) 1520 mm Hg, B 5) 0.52 atm, G-L 6) 2.75 L, Combined 7) 212 degrees F – boiling 32 degrees F - freezing

25. Ideal Gas Law

26. Avogadro’s Hypothesis
equal
Avogadro’s hypothesis states that ________ volumes of gases (under the same temp. and pressure conditions) contain _______ number of particles.
If containers have the same ____, ____, and ___, then they will have the same ____ of particles regardless of the _________ of the gas particle.
You might think that a small gas molecule would take up ______ space than a large gas molecule, but it ___________ at the same _________________ and ______________!!
equal
T P V #
size
more
doesn’t
temperature
pressure

27. Ideal Gas Law
An equation used to calculate the amount of gas in a container (in moles)
PV = nRT
V = in liters; T = in Kelvin; n = number of moles
R = ideal gas constant
The value of R changes depending on the unit of ____________ used in the equation:
pressure
R = 62.4 (mm Hg)(L)/(mole)(K) R = 8.31 (kPa)(L)/(mole)(K)
R = (atm.)(L)/(mole)(K) R = 2.45 (in. Hg)(L)/(mole)(K)

28. Ideal Gas Law Example PV = nRT V V = 120 L
6.5 moles of a gas has a pressure of 1.30 atmospheres and it has a temperature of 20˚Celsius. What is the volume of the gas?
PV = nRT V
( ) ( ) = ( ) ( ) ( )
1.30
6.5
0.0821
293 K
V = 120 L

29. Practice Ideal Gas Problem
How many moles of gas are there in a 7.3 liter balloon with a pressure of 1.5 atm and temperature of 395 K?

30. Ideal Gases Real Gas condense
Real gases, (like N2), will eventually ___________ into a liquid when the temperature gets too ____ or the pressure gets too _____.
If you want a gas to act more ideally, keep the temperature _____ and the pressure ______. That way, they will act more like an ideal gas.
The best real gas that cats like an ideal gas is __________. It doesn’t condense until the temperature gets to ______K.
low
high
high
low
helium 4
Real Gas

31. Exit Slip
How big is a balloon if the balloon is filled with 2 moles of nitrogen gas and has a pressure of 0.5 atm at a temperature of 350K?

32. Pressure & Dalton’s Law of Partial Pressure

33. How Temperature affects Vapor Pressure
Vapor Pressure is simply the push of a gas above its liquid.
As the temperature of a liquid increases, so does the ____________ of vapor particles.
More vapor particles cause more ____________, therefore _______ vapor pressure. [___________ Relationship: (T ↑ Vapor Pressure ↑)]
number
collisions
more
Direct

34. How Altitude affects Air Pressure
The higher up you go the ______ air molecules there are, so there are ______ collisions which will cause _____ pressure.
(______________ Relationship: As altitude ↑ pressure )
*Examples: This is the reason why your ears pop in ____________, ____________, or driving up and down large hills.
(Going deep under the water will also cause your ears to pop because of increasing __________ pressure.)
less
fewer
less
Inverse
elevators
planes
water

35. Diffusion high Perfume
The spreading out of a gas from _______ to _____ concentrations is called diffusion.
*Example: ___________ in a room spreads out
low
Perfume

36. Dalton’s Law of Partial Pressure
The ______ of each individual gas pressure equals the _______ gas pressure of the container.
P(total)= P1+P2+P3…
For a mixture of ideal gases, it is the number of moles of particles that is important, not identity.
sum
total

37. Partial Pressures Example
A container has 1 mole of oxygen and 3 moles of helium in it. The total pressure of the container is 2.4 atmospheres. What is the partial pressure of oxygen and helium?

38. Partial Pressures Example #2
If I place 3 moles of N2 and 4 moles of O2 in a 35 L container at a temperature of 25 degrees C, what will the pressure of the resulting mixture of gases be?

39. Partial Pressures Try (Tough)
Mixtures of helium and oxygen are used in the “air” tanks of underwater divers for deep dives. For a particular dive, 12 L of O2 at 25˚C and 1.0 atm and 46 L of He at 25˚C and 1.0 atm were pumped into a 5.0 L tank.
(1) Calculate the partial pressure of each gas
(2) Calculate the total pressure in the tank at 25˚C
*Hint: Manipulate Ideal Gas Equation:
Because partial pressures of each gas depends on moles of gas present, first calculate number of moles:
nO2 = (PV)/RT nHe = (PV)/RT
PO2 = (nRT)/V PHe = (nRT)/V

40. Exit Slip
A balloon has a mix of 3 moles of oxygen gas and 4 moles of helium gas. If the total pressure is 9.0 atm, what is the partial pressure of each gas?

41. Few selected answers from last year

42. Gas Law Practice 3 (Check yo answers!)
5. Box mL (remember temp should be in Kelvin!) 7. Box mm Hg 9. 3 atm psi K atm kPa psi K
*can cross out one of the #10’s

43. Acc Gas Law Practice 3 (Check yo answers!)
4. Box mL 6. Box mm Hg 8. 3 atm psi K K L kPa psi K

44. Gas Law Practice 4
gallons
4. 2L (this one is tricky!!!) normally its 4L but it’s a closed jar, so the jar can’t expand (if there is enough pressure the can would  _____)
5. a) 0.95 moles
b) 77.9 L
c) 406 K
d) kPa
*I think, check with me if there is something is wrong!

45. Answers to Gas Law Practice 5
2. Air P decreases (less air molecules)
3. Heating  more gas particles  more particles mean more pressure
PN2 = 2.96 atm PH2 = 1.97 atm
Ptot = 4.93 atm
5. PCO2 = atm
b. PH2 = atm
7. PO2 = 2.4 atm PHe = 9.3 atm Ptot = 11.7 atm
(the number of moles is 0.49 mol O2 and 1.9 mol He  it’s in a new container with a volume of 5.0L)