📚 What are Physical Changes?
A physical change is when a substance changes its appearance, but it's still the same substance. Think of it like cutting paper! The paper is still paper, just in smaller pieces.
- 🧊Melting ice: 💧 Ice changing from solid to liquid is a physical change. It's still water ($H_2O$).
- ✂️Cutting paper: 📄 Ripping or cutting paper changes its size and shape, but it's still paper.
- 🧱Breaking a brick: 🔨 Breaking a brick into smaller pieces is a physical change; it's still brick.
🧪 What are Chemical Changes?
A chemical change is when a substance is changed into a new substance. This often involves a chemical reaction. Think of baking a cake – you can't unbake it!
- 🔥Burning wood: 🪵 When wood burns, it turns into ash and smoke. It's no longer wood.
- 🍳Cooking an egg: 🥚 When you cook an egg, it changes its texture and composition. You can't turn it back into a raw egg.
- 🍂Rusting of iron: 🔩 When iron rusts, it reacts with oxygen to form iron oxide (rust). This is a new substance.
📝 Chemical vs. Physical Changes: The Table
| Feature |
Physical Change |
Chemical Change |
| Definition |
Changes appearance without changing the substance. |
Creates a new substance. |
| Reversibility |
Often easily reversible. |
Usually not easily reversible. |
| Composition |
Composition remains the same. |
Composition changes. |
| Examples |
Melting, cutting, dissolving. |
Burning, rusting, cooking. |
💡 Key Takeaways
- 🧊Physical changes: 💧 Alter the form or appearance of a substance without changing its chemical identity.
- 🧪Chemical changes: 🧬 Result in the formation of new substances with different properties.
- 🔥Look for clues: 🔍 Signs like color change, gas production, or heat release often indicate a chemical change.