Physical Change:
* Definition: A change in the form or appearance of a substance, but not its chemical composition.
* Examples:
* Melting ice: Water changes from solid to liquid, but it's still H2O.
* Boiling water: Water changes from liquid to gas, but it's still H2O.
* Cutting paper: Changes the shape of the paper but not its chemical composition.
* Dissolving sugar in water: Sugar molecules are dispersed but still maintain their chemical structure.
* Key Characteristics:
* Reversible: Most physical changes can be reversed.
* No new substances formed: The chemical composition remains the same.
* Usually involve changes in state or appearance.
Chemical Change:
* Definition: A change in the chemical composition of a substance, resulting in the formation of new substances with different properties.
* Examples:
* Burning wood: Wood reacts with oxygen to produce ash, carbon dioxide, and water.
* Rusting of iron: Iron reacts with oxygen and water to form iron oxide (rust).
* Baking a cake: Ingredients combine and undergo chemical reactions to form a new substance.
* Cooking an egg: The proteins in the egg change chemically when heated, altering its texture and appearance.
* Key Characteristics:
* Irreversible: Difficult or impossible to reverse without further chemical reactions.
* New substances formed: The chemical composition changes.
* Often involve energy changes (heat, light, etc.).
In Summary:
| Feature | Physical Change | Chemical Change |
|----------------------|-------------------------------------------|-------------------------------------------|
| Chemical Composition | Remains the same | Changes, new substances are formed |
| Reversibility | Often reversible | Usually irreversible |
| Energy Changes | May involve energy changes, but not always | Often involve energy changes |
| Examples | Melting, freezing, boiling, dissolving | Burning, rusting, cooking, baking |
Remember, a physical change involves only a change in form or appearance, while a chemical change results in the formation of entirely new substances with different properties.
