A/C System Physical Principles

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The four known states of water also apply to A/C system refrigerants.

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Gaseous (invisible)
Vapor
Liquid
Solid

When water is heated in a container (heat absorption), rising water vapor becomes visible. If the vapor continues to heat up through heat absorption, the visible vapor turns into invisible gas. The process is reversible. If heat is extracted from water in gaseous form -A-, it changes first to vapor -B-, then to water and finally to ice.

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A - Heat Absorption

B - Heat Emission

Heat Always Transfers from Warm to Cold Matter

All matter consists of a mass of moving molecules. The fast moving molecules of a warmer substance give off some of their energy to the cooler and thus slower molecules. As a result, the molecular motion of the warmer substance slows down and that of the colder substance is accelerated. This process continues until the molecules of both substances are moving at the same speed. They are then at the same temperature and no more heat transfer occurs.