Physical Change
* Definition: A change in the form or appearance of a substance, but not its chemical composition.
* Key Characteristics:
* No new substances are formed.
* Changes are usually reversible.
* Involves changes in states of matter (solid, liquid, gas) or physical properties like shape, size, or texture.
* Examples:
* Melting ice (solid to liquid)
* Boiling water (liquid to gas)
* Cutting paper
* Dissolving sugar in water (sugar molecules remain unchanged)
* Crushing a rock
Chemical Change
* Definition: A change where a new substance is formed with different chemical properties.
* Key Characteristics:
* A new substance is formed with a different chemical composition.
* Changes are usually irreversible (or very difficult to reverse).
* Often accompanied by:
* Heat or light production (exothermic)
* Gas production (bubbling)
* Color change
* Formation of a precipitate (solid forming in a solution)
* Examples:
* Burning wood (wood reacts with oxygen to form ash, carbon dioxide, and water)
* Rusting of iron (iron reacts with oxygen and water to form iron oxide)
* Cooking an egg (proteins change structure)
* Baking a cake (ingredients react to form a new substance)
* Souring milk (bacteria break down lactose into lactic acid)
In a Nutshell:
Think of it this way:
* Physical changes are like rearranging furniture in a room. The room itself remains the same.
* Chemical changes are like building a new house. You're creating something entirely different with new properties.
