1. Starter S-146
List five properties of gases.

2. Chapter 14
The Behavior of Gases

3. Chapter 14
14.1 Properties of Gases

4. 14.1 Properties of Gases
Gases are easily squeezed into a smaller volume
Compressibility – how
much the volume
decreases under
pressure
Air bags are absorb energy by
compressing a gas

5. 14.1 Properties of Gases
Gases can be compressed because the actual particles take up very little of the volume

6. 14.1 Properties of Gases Four variables are used to describe gases
Pressure (P) – force per unit area on the container
Volume (V) – in liters, how much space the gas take up
Temperature (T) – average kinetic energy
Number of Moles (n) – how much of the gas is present

7. Chapter 14
14.2 The Gas Laws

8. 14.2 The Gas Laws Robert Boyle Boyle’s Law – If temperature is
kept constant, as pressure
increases the volume
decreases
So if T is constant or

9. 14.2 The Gas Laws Since the equation is equal to a constant
This is used to compare values as long as the temperature and the number of moles remain constant

10. 14.2 The Gas Laws Jacques Charles Charles’s Law – If pressure is
kept constant, at temperature
increases, pressure also
increases
That is or

11. 14.2 The Gas Laws Since the equation is equal to a constant
This is used to compare values as long as the pressure and the number of moles remain constant
Temperature must always be calculated in Kelvin in all gas calculations

12. 14.2 The Gas Laws Joseph Gay-Lussac Gay-Lussac’s Law – If volume
is constant, when the
temperature increases,
pressure increases
That is or
Simulation

13. 14.2 The Gas Laws Since the equation is equal to a constant
This is used to compare values as long as the volume and the number of moles remain constant
Temperature is in Kelvin

14. 14.2 The Gas Laws
Combined Gas Law – all three relationships are combined into
This equation can be used to solve relationships that involve any combination of these three variables
Just remove any variable that does not change

15. 14.2 The Gas Laws
Example – a sample of oxygen gas at STP is heated to 50.0oC at a constant volume, what is the new pressure?
What stays constant?

16. 14.2 The Gas Laws
Example – If 40.0 mL of nitrogen gas at 812mmHg and 75.0oC is cooled to oC and has the pressure reduced to 125mmHg, what is the new volume?

17. Chapter 14
14.3 Ideal Gas

18. 14.3 Ideal Gas
Avogadro’s Law – if the temperature and pressure are held constant, an increase in gas particles (moles) will cause an increase in the volume
This can be written as
Simulation

19. 14.3 Ideal Gas The ideal gas law combines all
the laws into one equation
R is a constant
Usually written as

20. 14.3 Ideal Gas
A container has 2,240,000 L of methane gas (CH4) at a pressure of 1500 kPa and a temperature of 42oC.
How many moles of gas are in the container?
How many grams of gas are in the container?

21. 14.3 Ideal Gas
An ideal gas – is an imaginary gas that always follows the ideal gas law
In a real gas
Particles take up volume
Force exist between particles
So real gases deviate from the an ideal gas especially at
Low temperature
High pressure

22. 14.4 Gases: Mixtures and Movements
Chapter 14
14.4 Gases: Mixtures and Movements

23. 14.4 Gases: Mixtures and Movements
Dalton’s Law of Partial Pressure – in a mixture of gases, the total pressure is the sum of the partial pressures of the gases
Since the temperatures and volumes must be the same for each gas
All that matters is the number of moles of gas present

24. 14.4 Gases: Mixtures and Movements
Dalton’s Law of Partial Pressure – in a mixture of gases, the total pressure is the sum of the partial pressures of the gases
Since the temperatures and volumes must be the same for each gas
All that matters is the number of moles of gas present

25. 14.4 Gases: Mixtures and Movements
The total air pressure is the sum of the partial pressures of the different gases
Composition of Dry Air
Component
Volume (%)
Partial Pressure (kPa)
Nitrogen
78.08
79.11
Oxygen
20.95
21.22
Carbon Dioxide
0.04
Other Gases
0.93
0.95
Total
100.00
101.32

26. 14.4 Gases: Mixtures and Movements
The minimum partial pressure of oxygen needed for a human is about 16kPa
Partial pressures are written with a subscript
This can be calculated using the ideal gas law

27. 14.4 Gases: Mixtures and Movements
Thomas Graham
Diffusion – tendency of particles
to move toward areas of
lower concentration
Effusion - is the process in
which individual molecules
flow through a hole without
collisions between molecules
Simulation

28. 14.4 Gases: Mixtures and Movements
Graham’s Law of Effusion – the rate of effusion of a gas is inversely proportional to the square root of the gas’s molar mass
Can be written
If two objects are at the same temperature they must have the same kinetic energy

29. 14.4 Gases: Mixtures and Movements
So a larger molecule must be moving slower