Gas Laws

Kinetic Theory: A Review All molecules have kinetic energy Gases have more kinetic energy than solids and liquids The molecules in a gas are constantly colliding with each other and the sides of their containers Gases will expand to fill the container that they are in Gases CAN be COMPRESSED

Charles’ Law Charles’ Law states that “the volume of a gas is directly proportional to the temperature of the gas.” In other words, gases take up MORE space when you add HEAT (kinetic energy)

Charles’ Law (contd.) Also, when you decrease the volume of the container that a gas is in, you will cause that gas to collide with itself and the walls of the container more. This increases kinetic energy.

Charles’ Law illustrated: Note the increase in temperature (K).

Pressure and Volume The pressure that a gas is being stored at will also affect its volume Since gases can be compressed, if we put pressure on gas molecules, they move closer together and they take up less space

Boyle’s Law Boyle’s Law states that “the pressure on a gas is INVERSELY proportional to the volume of a gas.” In other words, if you add pressure, the gas takes up less space. If you decrease pressure, the gas takes up more space.

Boyle’s Law Illustrated Note that as the pressure goes up, the volume goes down.

Review Questions: Gas Laws Unlike solids or liquids, gases have no definite __________ and __________. What are two factors that will affect how much volume a gas takes up? Is Charles’ Law a DIRECT or INVERSE relationship? What about Boyle’s Law? What happens to the molecules of a gas when you heat the gas?

Gas Law Practice Problems

1. A sample of nitrogen inside a rigid metal container under 3 1. A sample of nitrogen inside a rigid metal container under 3.00 atm of pressure at 20.0°C is place inside an oven whose temperature is 50.0 °C. What is the pressure of the nitrogen after its temperature is increased?

2. A container of oxygen has a volume of 30. 0 mL and a pressure of 4 2. A container of oxygen has a volume of 30.0 mL and a pressure of 4.00 atm. If the pressure of the oxygen is reduced to 2.50 atm, what is the new volume of the oxygen gas?

What pressure is required to compress 196 What pressure is required to compress 196.0 liters of air at STP into a cylinder whose volume is 26.0 liters?

4. What change in volume results if 60. 0mL of gas is cooled from 33 4. What change in volume results if 60.0mL of gas is cooled from 33.0 °C to 5.00 °C?

5. A gas occupies 1.0L at 0.0 °C . What is the volume at 333.0 °C?