When a liquid is cooled enough that its molecules' movements are slowed down and arranged into a fixed position, the process is called "freezing." Freezing is the phase transition of a substance from its liquid state to its solid state, in which the particles lose energy and become more ordered, resulting in a reduction in the substance's temperature and volume. The molecules in the liquid are arranged in a random pattern, but as they lose energy and begin to slow down, they become more ordered and eventually form a crystal lattice in the solid state.