Chemical Reactions
Summary: Processes where atoms rearrange to form new substances with different properties. Tags: concepts chemistry Created: 2026-04-23T00:00:00Z Last Updated: 2026-04-23T00:00:00Z
Content
A chemical reaction is a change where atoms are rearranged to create new substances. Elements and compounds participate, producing new materials with transferred energy. Most are irreversible.
Evidence: gas release, temperature change, color change, flames, smells, sounds.
Types:
- Exothermic: releases energy (feels hot)
- Endothermic: absorbs energy (feels cold)
- Displacement: more reactive metal replaces less reactive
- Neutralization: acid + alkali → salt + water
Catalysts speed up reactions without being used up.
Contrast with Physical Changes which are reversible and don’t form new substances.