The Behavior of Gases

1
The Behavior of Gases

• Its a Gas, Gas, Gas!

2
Properties of Gas

• Gases are easily compressed because of the space
  between the particles in the gas.
• The amount of gas, volume and temperature affect
  the pressure of a gas.
• Doubling the number of particles in the container
  would double the pressure on a contained gas at
  constant temperature.
• Boyles Law P1V1 P2V2

3

• A) 50 kPa
• B) 33 kPa
• C) inverse proportion - as one increases the
  other decreases

4

• Reducing the volume of a contained gas to one
  third, while holding temperature constant, causes
  pressure to become tripled.

5

• A gas occupies a volume of 2.50 L at a pressure
  of 350.0 kPa. If the temperature remains
  constant, what volume would the gas occupy at
  1750 kPa?
• V V2 ? V1 2.50 L
  P1 350.0 kPa
  P2 1750 kPa
• F P1V1 P2V2
• S (350.0 kPa)(2.50 L) (1750 kPa)V2
• A V2 0.500 L

6
Boyles Law Temperature

• If the volume of a container of gas is reduced,
  the pressure inside the container will increase.
• The graph of several pressure-volume readings on
  a contained gas at constant temperature would be
  a curved line.
• If a balloon is squeezed, the pressure of the gas
  inside the balloon increases.
• Temperature is directly proportional to the
  average kinetic energy of the particles in a
  substance.

7

• As the temperature of the gas in a balloon
  decreases,
• the average kinetic energy of the gas decreases.
• Absolute zero is the temperature at which the
  average kinetic energy of particles would
  theoretically be zero.
• This is the lowest possible temperature.
  (-273.15C)

8

• To get kelvins subtract 273 from the C.
• To get C add 273 to the kelvins.
• A temperature of -25C is equivalent to 248 K.
• A temperature of 295 K is equivalent to 22 C.

9

• When the Kelvin temperature of an enclosed gas
  doubles, the particles of the gas move faster.
• The Kelvin temperature must be used when working
  with proportions.

10

• Problem A balloon contains 30.0 L of helium gas
  at 103 kPa. What is the volume of the helium when
  the balloon rises to an altitude where the
  temperature stays the same but the pressure is
  only 25.0 kPa?
• V V2 ? P1 103 kPa
  V1 30.0 L P2 25.0
  kPa
• F P1V1 P2V2
• S (103 kPa)(30.0 L) (25.0 kPa)V2
• A V2 124 kPa

11
Charles Law

• when the temperature is
  expressed in kelvins.
• At constant pressure, the volume of a fixed mass
  of gas and its Kelvin temperature are said to be
  directly related.
• If a balloon is heated, the volume of the air in
  the balloon increases if the pressure is constant.

12

• The temperature of 6.24 L of a gas is increased
  from 125 K to 250. K at constant pressure. What
  is the new volume of the gas?
• V V2 ? V1 6.24 L
• T1 125 K T2 250. K
• F
• S
• A V2 12.48 L

13

• A) kelvins
• B) increases
• C) 0 L

14
Combined Gas Law

• Gay-Lussacs Law If the Kelvin temperature of
  a gas in a closed container increases the
  pressure of the gas increases proportionally.
• As the temperature of a fixed volume of a gas
  increases, the pressure will increase.

15

• A sample of chlorine gas has a pressure of 9.99
  kPa at 27C.
• What will its pressure be at 627C if its volume
  remains constant?
• V P2 ? P1 9.99 kPa
• T1 300. K T2 900.
  K
• F
• S
• A P2 29.97 kPa

16

• The Combined Gas Law
• The combined gas law relates temperature,
  pressure, and volume.

17

• If a sample of oxygen occupies a volume of 6.00 L
  at a pressure of 68.0 kPa and a temperature of
  264 K, what volume would this sample occupy at
  204 kPa and 528 K?
• V V2 ? V1 6.00 L
  P1 68.0 kPa T1
  264 K
• P2 204 kPa T2 528 K
• F
• S
• A V2 4.00 L