Unit 5 - Gas Laws

Unit 5 - Gas Laws

by S Harris

​Learning Target

​I know...

• how to describe the properties of a gas. (define its shape and volume)

Success Criteria

​I can...

• ​describe the Boyle’s and Charles’ Laws relating temperature or volume to pressure.

​Recap

​There are 4 states of matter

• plasma: most abundant form of matter in the universe (~99%)

• ​​solid: definite shape and volume

• ​liquid: definite volume, no definite shape

• ​gas: no definite shape, no definite volume (can be compressed)

​Gas particles have constant, random motion (allows them to fill up their container)

​Recap Continued

Kinetic energy = energy of motion

​The kinetic molecular theory says that:

​As temperature increases, kinetic energy (particle motion) increases

Multiple Choice

Which one of the images represents the particle motion of a gas?

Multiple Choice

Which one of the terms below does not describe the motion of particles in a gas?

• vibrating

• random

• constant

What is pressure?

Pressure is the result of a force distributed over an area (equation: P = F ÷ A)

• Collisions between particles of a gas and the walls of the container cause the pressure in a closed container of gas to increase

  The more frequent the collisions the greater the pressure of the gas

​Real World Examples

​A balloon and bicycle tire are considered to be containers.

They remain inflated because of collisions the air particles have with the walls of their container.

​Factors that affect the pressure of an enclosed gas are its:

1. ​temperature

2. ​volume

3. ​number of particles

Multiple Choice

which of these does not affect pressure?

• number of gas particles

• temperature

• time

• volume of the gas

Multiple Choice

Increasing the number of gas particle collisions inside of the container will cause the pressure of the container to ____.

• increase

• decrease

​Factors that Affect Gas Pressure

1.  Temperature

As the temperature rises, the average kinetic energy of the particles in the air increases

• The particles move faster and collide more often.

• Raising the temperature of a gas will increase its pressure if the volume of the gas and the number of particles are constant

​2. Volume

• Reducing the volume of a gas increases its pressure if the temperature of the gas and the number of particles are constant

• The more particles there are in the same volume, the greater the number of collisions and the greater the pressure

• Increasing the number of particles will increase the pressure of a gas if the temperature and the volume are constant

3.  Number of Particles

​Boyle’s Law

​Boyle’s law states that the volume of a gas is inversely proportional to its pressure if the temperature is constant

​Graph description:

• ​pressure and volume are being related

• ​curved graph

• ​temperature is being held constant, so it is not included in the graph

​Equation

​Relationship

​Think about it...

Imagine you have a syringe and you place your finger at the tip of a syringe so that no gas can escape. Now you start to push down on the plunger of the syringe.

What will happen to the volume of the syringe?

​What happens to the pressure?

​Answer

Decreasing the volume will increase the number of collisions that the gas particles have with the syringe container. This will increase the pressure in the syringe.

​Charles’s Law

​Jacques Charles showed that the volume of a gas increases at the same rate as the temperature of the gas

• Charles’s Law states that the volume of a gas is directly proportional to its temperature in Kelvin if the pressure is constant

​Graph description:

• ​temperature and volume are being related

• ​linear graph

• ​pressure is being held constant, so it is not included in the graph

​Equation

​Relationship

​Think about it...

Imaging putting a balloon filled with gas in liquid nitrogen (− 196 °C or− 320 °F).

What will happen to the temperature of the gas in the balloon?

​What happens to the volume of the balloon?

​Answer

The temperature will decrease and because volume and temperature are directly proportional, the volume will also decrease.

Multiple Choice

The graph is demonstrating which gas law?

• Boyle

• Charles

Multiple Choice

Charles' gas law says that temperature and volume are _____ proportional.

• directly

• indirectly