Physical and Chemical Changes Worksheet | PDF | Chemical ... - Free Printable

Let’s go through each item one by one to decide if it’s a physical change or a chemical change.

Remember:
- Physical change: The substance stays the same — just changes shape, size, state (like solid to liquid), or mixes without reacting. You can often reverse it.
- Chemical change: A new substance is made. Often you see bubbles, heat, light, color change, or smell. Usually not easy to reverse.

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1. Sodium hydroxide dissolves in water.
→ Dissolving is usually physical. No new substance forms — just ions spread out in water.
✔ Physical

2. Hydrochloric acid reacts with potassium hydroxide to produce salt, water and heat.
→ “Reacts” + produces new substances (salt and water) + heat = chemical reaction.
✔ Chemical

3. A pellet of sodium is sliced in two.
→ Just cutting — still sodium. Shape changed, but no new substance.
✔ Physical

4. Water is heated and changed to steam.
→ Phase change: liquid → gas. Still H₂O. Reversible by cooling.
✔ Physical

5. Potassium chlorate decomposes to potassium chloride and oxygen gas.
→ One substance breaks into two different ones → new substances formed.
✔ Chemical

6. Iron rusts.
→ Rust is iron oxide — new substance formed from iron + oxygen.
✔ Chemical

7. When placed in H₂O, sodium metal catches on fire as hydrogen gas is liberated...
→ Fire + gas produced + new substances (hydrogen gas, sodium hydroxide) = chemical reaction.
✔ Chemical

8. Evaporation
→ Liquid turns to vapor — still same substance. Physical phase change.
✔ Physical

9. Ice melting
→ Solid to liquid — still water. Physical change.
✔ Physical

10. Milk sours
→ Bacteria turn lactose into lactic acid — new substance, sour taste, can’t easily reverse.
✔ Chemical

11. Sugar dissolves in water.
→ Sugar molecules mix with water — no reaction. Can evaporate water to get sugar back.
✔ Physical

12. Wood rotting
→ Decomposition by fungi/bacteria — wood turns into other compounds. New substances.
✔ Chemical

13. Pancakes cooking on a griddle
→ Heat causes proteins and starches to change permanently — browning, texture change. Chemical reactions (Maillard, etc.).
✔ Chemical *(Note: Student wrote “Physical” — that’s incorrect)*

14. Grass growing in a lawn
→ Growth involves many chemical reactions inside plant cells — photosynthesis, cell division, making new materials.
✔ Chemical *(Student wrote blank — should be Chemical)*

15. A tire is inflated with air.
→ Air pumped in — no reaction. Just pressure/volume change.
✔ Physical

16. Food is digested in the stomach.
→ Enzymes break down food into simpler chemicals — new substances formed (e.g., glucose from carbs).
✔ Chemical

17. Water is absorbed by a paper towel.
→ Capillary action — water moves into fibers. No chemical reaction.
✔ Physical

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Now let’s correct the student’s answers where needed:

- #13: Pancakes cooking → Chemical (not Physical)
- #14: Grass growing → Chemical (was blank)

All others are correctly labeled by the student.

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Final Answer:
1. Physical
2. Chemical
3. Physical
4. Physical
5. Chemical
6. Chemical
7. Chemical
8. Physical
9. Physical
10. Chemical
11. Physical
12. Chemical
13. Chemical
14. Chemical
15. Physical
16. Chemical
17. Physical