Physical and Chemical Changes
Matter can undergo physical or chemical changes, which describe how its properties or composition are altered.
Physical Changes
- Change in state or appearance without altering chemical composition
- Reversible in many cases
- Examples: Melting, boiling, freezing, dissolving, breaking, cutting
Chemical Changes
- Change that produces a new substance with different chemical properties
- Often irreversible under normal conditions
- Indicators: Color change, gas formation, precipitate formation, energy release/absorption
- Examples: Rusting of iron, combustion, baking a cake, digestion
Distinguishing Between Changes
| Feature | Physical Change | Chemical Change |
|---|---|---|
| Composition | Unchanged | Altered |
| Reversibility | Often reversible | Usually irreversible |
| Energy Change | Minor | Often significant |
| Examples | Ice melting, sugar dissolving | Iron rusting, wood burning |
Importance
- Understanding changes helps predict reaction outcomes, material behavior, and energy transfer
- Essential for laboratory experiments, chemical engineering, and everyday chemistry
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