phases of matter
Another way to classify matter is to describe it as a solid, a liquid, or a gas, which was done in the examples of solutions. These three descriptions, each implying that the matter has certain physical properties, represent the three phases of matter. A solid has a definite shape and a definite volume. Liquids ordinarily have a definite volume but not a definite shape; they take the shape of their containers. Gases have neither a definite shape nor a definite volume, and they expand to fill their containers. We encounter matter in each phase every day; in fact, we regularly encounter water in all three phases: ice solid , water liquid , and steam gas . We know from our experience with water that substances can change from one phase to another if the conditions are right. Typically, varying the temperature of a substance and, less commonly, the pressure exerted on it can cause a phase change, a physical process in which a substance goes from one phase to another Figure 1.4 "Boiling Water" . Phase changes have particular names depending on what phases are involved, as summarized in Table 1.1 "Phase Changes". Table 1.1 Phase Changes.