Educational worksheet for identifying physical and chemical changes, featuring examples and matching images to concepts like oxidation, fermentation, and combustion.

Let's solve the problem step by step.

---

Part 1: Identify whether each change is physical or chemical

We need to determine if each process involves a physical change (no new substance formed, only state or form changes) or a chemical change (new substances are formed due to chemical reactions).

| Change | Physical or Chemical? |
|-------|------------------------|
| Liquid water freezes and becomes a solid. | Physical – Only a change in state (liquid → solid), no new substance formed. |
| A metal object rusts and an orange substance appears. | Chemical – Rusting is oxidation of iron, forming iron oxide (a new substance). |
| Bacteria transforms milk into cheese. | Chemical – Fermentation by bacteria converts lactose into lactic acid, changing the composition. |
| We cut a piece of paper into smaller pieces. | Physical – Only size changes; no new substance formed. |
| Coal burns. | Chemical – Combustion produces CO₂, ash, and heat; new substances form. |
| Yeast makes bread rise. | Chemical – Yeast ferments sugars to produce CO₂ gas, causing dough to rise (fermentation). |
| We set our clothes to dry. | Physical – Water evaporates from clothes; only phase change (liquid → gas). |
| Fireworks | Chemical – Explosive reactions produce light, sound, and gases; new substances form. |
| We boil water to make tea. | Physical – Boiling water is a phase change; although tea extraction may involve some chemical changes, boiling itself is physical. |
| Digestion | Chemical – Food is broken down into simpler molecules via enzymes (e.g., starch → glucose); new substances form. |

---

✔ Final Answers for Part 1:

| Change | Physical or Chemical? |
|-------|------------------------|
| Liquid water freezes and becomes a solid. | Physical |
| A metal object rusts and an orange substance appears. | Chemical |
| Bacteria transforms milk into cheese. | Chemical |
| We cut a piece of paper into smaller pieces. | Physical |
| Coal burns. | Chemical |
| Yeast makes bread rise. | Chemical |
| We set our clothes to dry. | Physical |
| Fireworks | Chemical |
| We boil water to make tea. | Physical |
| Digestion | Chemical |

---

Part 2: Match the images to the correct chemical change

Now we match each image with the correct type of chemical change:

1. Candle burning
→ Combustion
*Explanation:* Burning wax reacts with oxygen to produce CO₂, water vapor, and light/heat. This is a classic combustion reaction.

2. Cut apple turning brown
→ Oxidation (natural)
*Explanation:* The apple’s flesh reacts with oxygen in the air, causing browning (enzymatic oxidation). This is natural oxidation.

3. Yogurt (or fermented milk product)
→ Fermentation
*Explanation:* Lactobacillus bacteria ferment lactose into lactic acid, turning milk into yogurt. This is fermentation.

4. Rusty nails
→ Oxidation (rust)
*Explanation:* Iron reacts with oxygen and moisture to form iron oxide (rust). This is a specific type of oxidation called rusting.

---

✔ Final Matching:

| Image | Chemical Change |
|------|-----------------|
| Candle | Combustion |
| Apple | Oxidation (natural) |
| Yogurt | Fermentation |
| Rusty nails | Oxidation (rust) |

---

✔ Summary

- Physical changes: Freezing water, cutting paper, drying clothes, boiling water.
- Chemical changes: Rusting, fermentation (cheese/bread), burning coal/fireworks, digestion.
- Image matches: Correctly paired as above.

Let me know if you'd like this formatted for printing or a worksheet!