In physics, matter exists in three primary states: solid, liquid, and gas. Each state has distinct properties. Solids have a fixed shape and volume, liquids have a definite volume but take the shape of their container, and gases have neither fixed shape nor volume. Plasma, often considered the fourth state, is a highly energized form of matter found in stars and lightning.
The changes between these states, such as melting, freezing, or evaporation, are influenced by temperature and pressure. These transitions are key to understanding physical processes in chemistry and physics, and have important applications in everything from weather patterns to engineering innovations.