Solids
| Property of solids | Why they are like this |
| They have a fixed shape and cannot flow | The particles cannot move from place to place |
| They cannot be compressed or squashed | The particles are close together and have no space to move into |
| Property of solids | They have a fixed shape and cannot flow |
|---|---|
| Why they are like this | The particles cannot move from place to place |
| Property of solids | They cannot be compressed or squashed |
|---|---|
| Why they are like this | The particles are close together and have no space to move into |
Liquids
| Property of liquids | Why they are like this |
| They flow and take the shape of their container | The particles can move around each other |
| They cannot be compressed or squashed | The particles are close together and have no space to move into |
| Property of liquids | They flow and take the shape of their container |
|---|---|
| Why they are like this | The particles can move around each other |
| Property of liquids | They cannot be compressed or squashed |
|---|---|
| Why they are like this | The particles are close together and have no space to move into |
Gases
| Property of gases | Why they are like this |
| They flow and completely fill their container | The particles can move quickly in all directions |
| They can be compressed or squashed | The particles are far apart and have space to move into |
| Property of gases | They flow and completely fill their container |
|---|---|
| Why they are like this | The particles can move quickly in all directions |
| Property of gases | They can be compressed or squashed |
|---|---|
| Why they are like this | The particles are far apart and have space to move into |
Pressure and temperature
Imagine a gas is trapped inside a container which has a fixed size (its volume cannot change).
If the gas is heated the particles will gain kinetic energy which will make them move faster. This means they will collide with the walls more frequently.
This causes the force on the walls of the container to increase and so the pressureForce exerted over an area. The greater the pressure, the greater the force exerted over the same area. increases.
Applications of kinetic theory
There are many places where we can use kinetic theory to describe what is happening to the gases involved.
Scuba diving
A diver uses tanks of air to breathe under water. When the tanks are filled, the air is transferred from the large volume of the outside air into the restricted, small volume of an oxygen tank. This means that as the volume decreases, the pressure inside the tanks increases as the particles are forced into a small space.
Tyre pressure
When a car's tyres (or a bicycle or motorbike etc) go flat, there is less air inside the tyres than we need there to be – the pressure inside the tyres is low.
To increase the air inside, we need to pump air in. As we pump air in, more particles are forced into a volume that stays the same and the pressure inside the tyres increases.
Aircraft
When an aircraft flies at a high altitude, the atmospheric pressure outside the cabin is very low. In fact, the pressure is so low that it would lead to altitude sickness in all of the passengers and crew. To avoid this happening, air is pumped from outside into the cabin, increasing the pressure inside and simulating the pressure we experience at ground level.
