Science
What is a Chemical Reaction?
A chemical reaction is a process where substances (the reactants) are transformed into different substances (the products) by rearranging their atoms. Bonds break and new ones form, creating new materials — like iron rusting, wood burning, or baking soda fizzing in vinegar.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains a chemical reaction.
Key things to understand
- 1In a reaction, atoms are rearranged: bonds in the starting substances break, and new bonds form to make new substances.
- 2No atoms are created or destroyed — they're just regrouped (the law of conservation of mass).
- 3Reactions often involve energy: some release it (burning), others absorb it.
- 4Signs a reaction happened: a colour change, gas bubbles, heat or light, or a solid forming.
- 5Catalysts can speed reactions up without being used up themselves.
Frequently asked questions
- What happens during a chemical reaction?
- The atoms in the reactants rearrange — old chemical bonds break and new ones form — turning the starting substances into different products.
- How can you tell a chemical reaction has occurred?
- Common signs include a colour change, bubbles of gas, a temperature change, light, or a new solid (a precipitate) forming.
- Are atoms lost in a reaction?
- No. Atoms are only rearranged, never created or destroyed — so the total mass stays the same (conservation of mass).