TEMPERATURE AND HEAT TRANSfER
When we heat the air in a vessel, we are increasing the kinetic energy of each particle, which means a higher average kinetic energy. As a result the gas particles move about faster, and they collide more frequently and more violently with their su rroundings. If the density of the gas particles (the number per unit volume) is quite ,large, then the hot gas can transport a great deal of heat (or thermal energy) from one place to another. The flow of energy in nature is from regions in which the energy content is high to those in which it is low; natural physical processes tend to even out the energy content, whether on a small scale or a large one, and in general large energy differences and large volumes of space over which energy is to be transported require long periods of time to smooth out the differences. This fact will help us to understand many aspects of the evolution of astronomical objects.
