Final answer:
Chemical changes alter a substance's molecular structure, leading to different properties. An example of a displacement or substitution reaction is when chlorine reacts with methane, resulting in chloromethane and hydrochloric acid.
Step-by-step explanation:
Explanation of Chemical Changes with Examples
Chemical changes occur when bonds are broken and/or formed between molecules or atoms, transforming one substance with certain properties into another with different properties. These changes often result in the production of heat or light, evolution of gases, color changes or the formation of a precipitate, and are usually difficult to reverse.
An example displacement or substitution reaction is when molecular chlorine reacts with methane (CH4) to produce chloromethane (CH3Cl) and hydrochloric acid (HCl). This represents a substitution reaction where one of the hydrogen atoms in methane is replaced by a chlorine atom.
Chemical equations are used to represent these transformations. For the given example, the balanced chemical equation would be CH4 + Cl2 → CH3Cl + HCl.