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What is a chemical reaction?
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Quick answer
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.
Key things to understand
- In a reaction, atoms are rearranged: bonds in the starting substances break, and new bonds form to make new substances.
- No atoms are created or destroyed — they're just regrouped (the law of conservation of mass).
- Reactions often involve energy: some release it (burning), others absorb it.
- Signs a reaction happened: a colour change, gas bubbles, heat or light, or a solid forming.
- Catalysts can speed reactions up without being used up themselves.
People also ask
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).
What happens in a chemical reaction?
Reactant molecules break and re-form bonds, rearranging atoms into new product molecules.
What are signs of a chemical reaction?
Color change, bubbles (gas), temperature change, light, or a new solid (precipitate) forming.
What's the difference between a physical and chemical change?
A physical change alters form (like melting); a chemical change creates new substances.