Physical Changes:
* No new substances are formed. The molecules themselves remain the same, just rearranged.
* Usually reversible. You can often get the original substance back.
* Change in appearance or state of matter. Examples: melting ice, boiling water, cutting paper, dissolving sugar in water.
Chemical Changes:
* New substances are formed. The molecules are broken apart and rearranged to form different molecules.
* Usually irreversible. Getting the original substance back requires a separate chemical reaction.
* Often accompanied by changes in color, odor, temperature, or gas production. Examples: burning wood, rusting metal, cooking an egg, baking a cake.
Here's a table to summarize the key differences:
| Feature | Physical Change | Chemical Change |
|------------------|-----------------|----------------|
| New substance? | No | Yes |
| Reversibility | Usually | Usually not |
| Changes observed | Appearance, state | Color, odor, gas |
Important Note: Some changes might seem like one type but are actually the other. For instance, dissolving salt in water appears to be a physical change (salt disappears), but it's actually a chemical change because the salt molecules interact with the water molecules, forming new bonds.
