Solids represent one of the three states of matter, liquids and gases representing, respectively, the other two. A solid has a fixed volume, high molecular density, a definite shape, and it foes not flow. These characteristics are exactly opposite to those of a gas. A liquid could be described as an intermediate form. A solid can change into a liquid by melting, a liquid changes into a solid by freezing, and some solids can change directly into a gas by sublimation. The temperature at which each of these events occurs is a fixed property of the solid. Chemists know these temperatures for pure substances; however, if the solid is not a pure substance, these temperature are harder to determine. In fact, an unexpected melting point is an indication that a substance is impure. The melting point and the freezing point are identical. A substance with a high melting...