Why Gases Exert Pressure
Gases exert pressure due to the constant motion of their molecules. When gas molecules move around in a container, they collide with the walls of the container. These collisions create a force per unit area, which results in pressure being exerted by the gas.

Constant Motion of Gas Molecules
- Gas molecules are in constant motion, moving randomly and colliding with each other and the walls of the container.
- This constant motion creates a force when the molecules collide with the walls of the container.

Impact of Collisions
- When gas molecules collide with the walls of the container, they exert a force on the walls.
- The force per unit area exerted by these collisions is what we perceive as pressure.

Pressure and Volume Relationship
- As the volume of the container decreases, the gas molecules have less space to move around, leading to more frequent collisions with the walls and an increase in pressure.
- Conversely, if the volume of the container increases, the gas molecules have more space to move around, resulting in fewer collisions and a decrease in pressure.

Temperature and Pressure Relationship
- Increasing the temperature of a gas increases the average speed of its molecules, leading to more frequent and forceful collisions with the walls of the container, thus increasing pressure.
- Decreasing the temperature decreases the average speed of gas molecules, resulting in fewer collisions and a decrease in pressure.
In conclusion, gases exert pressure due to the constant motion of their molecules, leading to collisions with the walls of the container. Understanding the relationship between volume, temperature, and pressure helps explain how gases exert pressure in different conditions.