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A solid is a state of matter in which the substance has a definite size and shape. The molecules that make up a solid are very close together and do not move about as they do in liquids and gases.
A solid becomes a liquid when it is heated to its melting point. A few solids change directly from a solid to a gas and this process is called sublimation.
Some substances are called semisolids. They are actually very thick liquids that seem like solids as they move much less than most liquids.
Some of the properties of solids are their shape, color, hardness, density (thickness), brittleness (how easily it can be smashed or broken into pieces), malleability, ductility, elasticity, tensile strength.