The particle model states that all matter is made up of particles which are in constant motion.
These particles are also attracted towards one another.
The three main points of the particle theory can be summarized as follows.
Temperature is a measure of the average energy of the particles. The faster the particles are moving the higher the temperature,. The slower the particles are moving the lower the temperature. At absolute zero which is -273°C or 0 K all particles have stopped moving. There is no energy and this is the coldest temperature in the universe.
The particle theory can be used to help explain the properties of solids, likes and gases.
|Physical state||Properties||Particle theory|
|Solid||Constant volume and fixed shape||The particles are close together and vibrate in fixed positions|
|Liquid||Constant volume and variable shape||The particles are close together and are moving over one another|
|Gas||Variable volume and variable shape||The particles are far apart and are rapidily moving past one another.|
Solids and liquids are very difficult to compress as the particles are close together. Gases however, can be easily compressed as their is plenty of space between the particles. This is why you can place compress the air in a bicycle pump even if your finger blocks the escaping air.
With cooler temperatures the particles slow down. This causes gas particles to condense. As the gas particles move past one another at a slower rate the attractive orces between them have a chance to act. Remember point three of the particle theory, "All particles are attracted towards one another"