States of matter. Illustration showing water in transition between three states (or phases) of matter: solid ice, liquid water, and steam or water vapour from a boiling kettle. Arrows show how each can be converted from one phase to another by freezing, melting, condensing, or evaporating. Molecules are in constant motion. In solids, the molecules have a strong attraction, are close together and have limited motion. In a liquid, the molecules have more energy, which enables them to overcome some of the attraction and move more freely. In a gas, attraction between particles is minimised and they move freely.