Educational worksheet identifying physical and chemical changes, featuring examples and images of processes like combustion, fermentation, and oxidation.

Let's solve the problem step by step.

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Part 1: Identify whether each change is physical or chemical

We need to determine if each process involves a physical change (no new substances 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, forming iron oxide (a new substance). |
| Bacteria transforms milk into cheese. | Chemical – Fermentation by bacteria changes milk proteins and lactose into cheese components. |
| We cut a piece of paper into smaller pieces. | Physical – Size changes, but no new substance is formed. |
| Coal burns. | Chemical – Combustion produces carbon dioxide, ash, etc. |
| Yeast makes bread rise. | Chemical – Yeast ferments sugars to produce carbon dioxide (gas), causing the dough to rise. |
| We set our clothes to dry. | Physical – Water evaporates from clothes; no new substance formed. |
| Fireworks | Chemical – Explosions involve rapid chemical reactions producing light, sound, and gases. |
| We boil water to make tea. | Physical – Water changes from liquid to vapor (boiling), though it may dissolve tea compounds (which could be chemical), but boiling itself is physical. |
| Digestion | Chemical – Food is broken down into simpler molecules via enzymes (e.g., starch → glucose). |

✔ Final Table Answer:

| 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 |

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Part 2: Match the images to the correct chemical change

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

#### Image 1: Burning candle
- A candle burning involves combustion (burning of wax in oxygen).
- ✔ Answer: Combustion

#### Image 2: Cut apple turning brown
- The browning of an apple is due to oxidation (enzymatic browning when exposed to air).
- This is a natural oxidation process.
- ✔ Answer: Oxidation (natural)

#### Image 3: Yogurt in jars
- Yogurt is made by fermentation of milk by bacteria (like *Lactobacillus*), converting lactose to lactic acid.
- ✔ Answer: Fermentation

#### Image 4: Rusty nails
- Nails rusting is oxidation of iron, forming iron oxide (rust).
- ✔ Answer: Oxidation (rust)

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✔ Final Matching:

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

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🔍 Summary:

- Physical changes: Freezing, cutting paper, drying clothes, boiling water.
- Chemical changes: Rusting, fermentation, burning, fireworks, digestion, yeast rising.
- The images represent specific types of chemical changes: combustion, oxidation, fermentation, and rust.

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