How does kinetic energy relate to the states of matter?

1 Answer
Mar 29, 2016

In the solid phase, the particles are very close together and only vibrate in their fixed positions in the crystal lattice structure. Thus they only have low vibrational kinetic energy, since #E_k=1/2mv^2+1/2Iomega^2#.

In the liquid phase the particles have larger spaces between them and move around more freely and thus have larger kinetic energies.

In the gaseous phase, there are very large spaces between particles and they move very free and at very large velocities, hence they possess very large kinetic energies.

In particular, temperature can be defined in terms of the particle model to be a measure of the average kinetic energy of the particles. As we heat a substance we give more thermal energy to the particles which is converted to kinetic energy and hence they move faster and further apart. If we continue heating, eventually a phase change occurs, but during such a process the temperature (and hence kinetic energy) remains constant.