Energy - Kinetic Theory

The kinetic theory links the movements of particles to heat energy - the higher the temperature, the faster the movement. It also takes into account the forces between the particles. It is not perfect, but works well at senior high school if you make the assumptions that all of the particles are identical and that any collisions between particles or the particles and the wall of a container are elastic.

In senior high school, you need to be able to recognize simple diagrams to model the difference between solids, liquids and gasses.

To be honest, this should not be too taxing as it is really just revision of concepts you first met during senior high school. These usually give the impression that the kinetic theory deals with small numbers of particles as there are only ever a few seen in drawings.

This is not the case. It is really a statistical theory that describes what happens to large numbers of particles as the temperature changes. It also helps you to understand a little more about temperature which is really just a measure of the energy in a sample of particles. The lower the temperature, the lower the energy of the particles, so they move more slowly. The particles of solids, liquids and gasses have different amounts of energy. In solids, the particle motions are limited to vibrations as the particles have the least energy. In liquids and gasses, the particles can exchange places. The forces between the particles of a solid are greater than those between the particles of a liquid and in a gas, the forces between the particles are considered as being zero.

You will need to be able to apply the kinetic theory to describe and explain various phenomena in all three sciences. In physics, you are most likely to need to be able to explain that the transfer of energy by conduction, convection, evaporation and condensation involves particles, and how this transfer takes place. This could include the movement of the free electrons in a metal as well as the closeness of the metal atoms in the structure. Also, you should be able to use the idea that as particles move apart when fluids are heated, the fluid becomes less dense and then apply it to the formation of convection currents. Remember that the word fluid could mean either a gas or a liquid - many students use the words fluid and liquid to mean the same thing. It is possible that you may also be challenged to explain why evaporation has a cooling effect.