Educational worksheet for identifying physical and chemical changes in everyday occurrences.

To solve this worksheet, we need to determine whether each of the listed occurrences represents a physical change (P) or a chemical change (C). Here's the explanation and classification for each:

Physical Change (P)

- Definition: A physical change involves a change in the form or appearance of a substance without altering its chemical composition. No new substances are formed.

Chemical Change (C)

- Definition: A chemical change involves a transformation where one or more new substances are formed with different chemical properties. The original substances are altered at the molecular level.

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Solution:

1. Crushing a rock
- Explanation: Crushing a rock changes its shape but does not alter its chemical composition.
- Answer: P

2. Digesting food
- Explanation: Digestion involves breaking down complex molecules into simpler ones through chemical reactions, forming new substances.
- Answer: C

3. Water evaporating
- Explanation: Evaporation is a phase change from liquid to gas, which is a physical process as no new substances are formed.
- Answer: P

4. Fireworks exploding
- Explanation: Fireworks involve combustion, which is a chemical reaction producing light, heat, and new substances.
- Answer: C

5. Getting a haircut
- Explanation: Cutting hair only changes its length; no chemical alteration occurs.
- Answer: P

6. An ice cube melting
- Explanation: Melting is a phase change from solid to liquid, which is a physical process.
- Answer: P

7. A candle burning
- Explanation: Burning a candle involves combustion, a chemical reaction that produces carbon dioxide, water, and other byproducts.
- Answer: C

8. Salt dissolving in water
- Explanation: Dissolving salt in water separates sodium and chloride ions but does not create new substances.
- Answer: P

9. Silver tarnishing
- Explanation: Tarnishing is a chemical reaction where silver reacts with sulfur compounds in the air to form a layer of silver sulfide.
- Answer: C

10. Glass breaking
- Explanation: Breaking glass only changes its shape; no chemical alteration occurs.
- Answer: P

11. Hair bleaching
- Explanation: Bleaching hair involves chemical reactions that alter the pigment molecules, creating new substances.
- Answer: C

12. A bicycle rusting
- Explanation: Rusting is a chemical reaction where iron reacts with oxygen and water to form iron oxide (rust).
- Answer: C

13. Frying an egg
- Explanation: Frying an egg involves denaturing proteins through heat, which is a chemical change as new substances are formed.
- Answer: C

14. Baking soda reacting with vinegar
- Explanation: This reaction produces carbon dioxide gas, water, and sodium acetate, indicating a chemical change.
- Answer: C

15. Oil mixing with water
- Explanation: Mixing oil and water does not produce new substances; it is a physical mixture.
- Answer: P

16. Cutting grass
- Explanation: Cutting grass only changes its size; no chemical alteration occurs.
- Answer: P

17. Butter melting
- Explanation: Melting butter is a phase change from solid to liquid, which is a physical process.
- Answer: P

18. Ethanol evaporating
- Explanation: Evaporation of ethanol is a phase change from liquid to gas, which is a physical process.
- Answer: P

19. Grass growing
- Explanation: Grass growth involves photosynthesis, a chemical process where plants use sunlight to convert carbon dioxide and water into glucose and oxygen.
- Answer: C

20. A tire inflating
- Explanation: Inflating a tire involves compressing air into the tire, which is a physical change as no new substances are formed.
- Answer: P

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Final Answer:

```
1. P
2. C
3. P
4. C
5. P
6. P
7. C
8. P
9. C
10. P
11. C
12. C
13. C
14. C
15. P
16. P
17. P
18. P
19. C
20. P
```