(b) During the combustion of a match, cellulose in the match and oxygen from the air undergo a chemical change to form carbon dioxide and water vapor. In each of these examples, there is a change in the physical state, form, or properties of the substance, but no change in its chemical composition.įigure 1.20 (a) Copper and nitric acid undergo a chemical change to form copper nitrate and brown, gaseous nitrogen dioxide. Other examples of physical changes include magnetizing and demagnetizing metals (as is done with common antitheft security tags) and grinding solids into powders (which can sometimes yield noticeable changes in color). Physical changes are observed when wax melts, when sugar dissolves in coffee, and when steam condenses into liquid water ( Figure 1.18). A physical change is a change in the state or properties of matter without any accompanying change in the chemical identities of the substances contained in the matter. Other physical properties, such as the melting temperature of iron or the freezing temperature of water, can only be observed as matter undergoes a physical change. Some physical properties, such as density and color, may be observed without changing the physical state of the matter. Familiar examples of physical properties include density, color, hardness, melting and boiling points, and electrical conductivity. A physical property is a characteristic of matter that is not associated with a change in its chemical composition. The characteristics that distinguish one substance from another are called properties. Identify properties of matter as extensive or intensive.
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Identify properties of and changes in matter as physical or chemical.By the end of this section, you will be able to:
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