What type of change involves the formation of new substances and clues such as heat or gas production?

The formation of new substances is a defining characteristic of a chemical change. During a chemical reaction, the original substances, known as reactants, undergo a transformation that results in the creation of new substances, referred to as products. This process often involves the rearrangement of atoms and can include various indicators such as heat production, gas release, color change, or the formation of a precipitate.

For example, when vinegar reacts with baking soda, carbon dioxide gas is produced, indicating a chemical change. Similarly, heat changes, such as those seen in combustion reactions, also signal the occurrence of a chemical change. These indicators help distinguish chemical changes from physical changes, which do not alter the chemical composition of substances, merely their physical state or appearance.

While biological and mechanical changes can involve some transformations, they typically do not focus on chemical composition in the same way as chemical changes do, making chemical change the most accurate description for the formation of new substances coupled with the observed clues.