Chemical reaction
A chemical reaction is a process in which one or more substances (called reactants) change into new substances (called products).
During a chemical reaction:
The atoms are rearranged.
Old chemical bonds break.
New chemical bonds form.
No atoms are created or destroyed—they are simply rearranged into new combinations.
Signs that a chemical reaction has happened
A color change
Gas is produced (bubbles)
A solid (precipitate) forms
Heat or light is released or absorbed
A new smell is produced
Example
When iron reacts with oxygen and water, it forms rust.
Iron + Oxygen + Water → Rust
Another example is burning wood:
Wood + Oxygen → Carbon dioxide + Water vapor + Ash + Heat + Light
Everyday examples
Cooking an egg
Burning a candle
Rusting of iron
Baking a cake
Digestion of food
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