Physical Nature and States of Matter

Core concept

These physical properties translate into measurable characteristics: solids have high density and low compressibility, gases have low density and high compressibility, with liquids falling in between. The kinetic theory of matter explains that all particles possess kinetic energy and are in constant motion, with this energy increasing as temperature rises, which is why heating a substance generally causes it to move from solid to liquid to gas as intermolecular forces are progressively overcome.