Free Printable Physical and Chemical Properties and Changes Worksheets - Free Printable

Let's solve this worksheet step by step.

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A. Classify the following changes as physical or chemical.

We need to determine whether each change involves a physical (no new substance formed) or chemical (new substance formed) change.

1. Sodium hydroxide dissolves in water
→ Dissolving is a physical change because NaOH breaks apart into ions but no new substance is formed. It can be reversed by evaporation.
✔ Physical Change

2. HCl reacts with KOH to produce salt, water, and heat
→ This is a neutralization reaction: HCl + KOH → KCl + H₂O + heat. New substances (salt and water) are formed.
✔ Chemical Change

3. A pellet of sodium is sliced into two
→ Cutting the sodium only changes its size and shape; no new substance is formed.
✔ Physical Change

4. Water is heated and changed into steam
→ This is a phase change from liquid to gas. No new substance is formed.
✔ Physical Change

5. Two substances are mixed, and light is produced
→ Light production is a sign of a chemical reaction (e.g., combustion or chemiluminescence). Energy release indicates a chemical change.
✔ Chemical Change

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B. Read each scenario. Decide whether a physical or chemical change has occurred and give evidence for your decision.

| Scenario | Physical or Chemical Change? | Evidence |
|--------|-------------------------------|---------|
| A student removes a loaf of hot bread from the oven... | Physical Change | He just made a mechanical mixture and made buttered toast. All the ingredients are still the same, meaning it is a physical change. |
| Your friend decides to toast a piece of bread but leaves it in the toaster too long. The bread is black, and the kitchen is full of smoke. | Chemical Change | The bread turns black and produces smoke, indicating burning (combustion), which forms new substances like carbon and gases. |
| You forgot to dry the bread knife when you washed it, and reddish-brown spots appeared. | Chemical Change | The reddish-brown spots are rust (iron oxide), formed when iron reacts with oxygen and water. This is a chemical reaction. |
| You blow dry your wet hair. | Physical Change | Water evaporates from hair, changing from liquid to vapor. No new substances are formed; it’s just a phase change. |
| In baking biscuits and bread, the baking powder reacts to release carbon dioxide bubbles. The carbon dioxide bubbles cause the dough to rise. | Chemical Change | Baking powder undergoes a chemical reaction (usually involving an acid-base reaction) to produce CO₂ gas. This gas causes the dough to rise, and the reaction cannot be easily reversed. |

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✔ Final Answers:

#### Part A:
1. Physical
2. Chemical
3. Physical
4. Physical
5. Chemical

#### Part B:

| Scenario | Physical or Chemical Change? | Evidence |
|--------|-------------------------------|---------|
| Toasting bread too long → black and smoky | Chemical Change | Blackened bread and smoke indicate combustion and formation of new substances. |
| Rust on knife | Chemical Change | Rust (iron oxide) is a new substance formed by oxidation. |
| Blow drying hair | Physical Change | Only water evaporates; no new substances are formed. |
| Baking powder releasing CO₂ | Chemical Change | Gas production from a chemical reaction in baking powder. |

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✔ Key Concept Reminder:
- Physical changes involve changes in state, shape, or size — no new substances form.
- Chemical changes involve formation of new substances, often with color change, gas production, temperature change, or odor.

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