Chemical Changes Examples Worksheet - Free Printable

Chemical Changes in Matter – Solved Worksheet

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#### Part 1: Circle the examples of items that changed chemically.

Chemical changes involve a transformation where the substance becomes something new, and the change cannot be reversed. This usually involves breaking or forming chemical bonds.

Let’s go through each item:

1. Wood that's been chopped → *Physical change* (size changed, but still wood). ✘
2. Clay rolled into a ball → *Physical change* (shape changed, no new substance). ✘
3. Food spoiled → ✔ Chemical change (bacteria cause decomposition; new substances form).
4. Mixed baking soda and vinegar (make a volcano erupt) → ✔ Chemical change (produces carbon dioxide gas, water, and salt).
5. Fried egg → ✔ Chemical change (heat denatures proteins; irreversible).
6. Fireworks exploded → ✔ Chemical change (combustion produces light, sound, gases).
7. Burned wood → ✔ Chemical change (combustion creates ash, smoke, CO₂).
8. Paper that has been cut → *Physical change* (only size changed). ✘
9. Rusted nail → ✔ Chemical change (iron reacts with oxygen to form iron oxide).
10. Broken glass → *Physical change* (shattered, but still glass). ✘
11. Mentos dropped in soda → ✔ Chemical change (reaction between sugar and citric acid causes rapid CO₂ release).
12. A crushed can → *Physical change* (compressed, but still aluminum). ✘

✔ Items that underwent chemical changes (to circle):
- food spoiled
- mixed baking soda and vinegar
- fried egg
- fireworks exploded
- burned wood
- rusted nail
- Mentos dropped in soda

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#### Part 2: Give an example where matter has been changed chemically by the following.

Now provide one example for each factor that causes a chemical change.

1. Heat
→ Cooking an egg (proteins denature and form new structures).
*(Or: Burning paper, roasting coffee beans)*

2. Air
→ Iron rusting (iron reacts with oxygen in air to form rust).
*(Or: Apple browning when exposed to air)*

3. Water
→ Baking soda reacting with water and vinegar (though water is part of the mix, it helps dissolve and react).
Better example: Dissolving metal in water (e.g., sodium reacting violently with water to produce hydrogen gas).
*(Or: Hydrolysis of certain compounds like starch breaking down in water with enzymes)*

4. Mixing substances
→ Mixing baking soda and vinegar (produces carbon dioxide gas).
*(Or: Mixing bleach and ammonia – dangerous, but creates toxic gas)*

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✔ Final Answers:

#### Circle these:
- food spoiled
- mixed baking soda and vinegar
- fried egg
- fireworks exploded
- burned wood
- rusted nail
- Mentos dropped in soda

#### Fill-in-the-blanks:
1. heat → cooking an egg
2. air → iron rusting
3. water → sodium reacting with water
4. mixing substances → baking soda and vinegar reacting

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💡 Tip: A good way to remember chemical changes: Look for signs like:
- Color change
- Gas production
- Formation of a precipitate
- Change in odor
- Irreversibility
- Energy released (light, heat)

This worksheet helps students distinguish between physical and chemical changes — a key concept in chemistry!