To determine whether an equation represents a physical change or a chemical change, one must look at the nature of the substances involved and the process described.
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Physical changes involve changes in state or appearance but do not alter the chemical composition of the substances. Common examples include melting, freezing, boiling, and dissolving.
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Chemical changes involve a transformation that alters the chemical composition of the substances, leading to the formation of new substances. Examples include rusting, combustion, and reactions that produce a gas or precipitate.
If you provide me with specific equations, I can help you identify which one represents a physical change.