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Phase Transitions

A phase transition typically describes the change between solid, liquid, and gaseous states of matter. In less common cases, a transition to plasma.

A phase transition graph with temperature against pressure. The 3 phases of matter, solid, liquid, and gas, cover different temperatures and pressures. The phase of matter is solid, at a low temperature from low to high pressures. The phase of matter is liquid, at intermediate to high temperatures and pressures. The phase of matter is gas, at low pressure with low to intermediate temperatures, and at high temperature with low to intermediate pressures. There are 3 phase transition lines which are between solid and liquid, liquid and gas, and solid and gas. Changing from a solid to liquid is melting, and the opposite transition is freezing. Changing from liquid to gas is vaporization, and the opposite transition is condensation. Changing from a solid to a gas is sublimation. The triple point is where all 3 phase transition lines cross, and this point is a low temperature and pressure. The critical point is where the phase transition line between liquid and gas stops, and this point is at a high temperature and pressure.

Figure 1: Phase transition temperatures and the physical state of a substance.