States of matter. Computer illustration showing the three states of matter (solid, liquid and gas) in a petri dish, beaker and gas jar, respectively, with arrows showing how each can be converted to another and back again. 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 throughout the container.