A chemical change, also referred to as a chemical reaction, occurs when a substance undergoes a
transformation that results in the formation of one or more new compounds.
This transformation involves the breaking and forming of chemical bonds between atoms or
molecules.
In a chemical reaction, the original substances (reactants) are converted into new substances
(products) with different properties.
Key features of a chemical change include:
1. New substances formed: The reactants are transformed into entirely different products that
have different chemical properties.
2. Energy changes: Chemical reactions often release or absorb energy, in the form of heat, light,
or electricity.
3. Irreversibility: Most chemical changes are not easily reversible without further chemical
reactions. Unlike physical changes, chemical changes often involve complex processes that
cannot be undone simply by changing temperature or pressure.
4. Indicators of a chemical reaction: Signs of a chemical reaction can include:
o Change in color
o Formation of a gas (bubbles or fizzing)
o Precipitate formation (solid formed from liquids)
o Temperature change (exothermic or endothermic reactions)
o Emission of light or sound
Examples of chemical reactions include
burning of wood
rusting of iron
Digestion of food.
In each of these examples, the original substance is chemically transformed into new products with
different properties.
