Let’s go step by step to figure out whether each event is a
physical change or a
chemical change, and then give evidence for our answer.
First, remember:
- A
physical change means the substance looks different but is still the same stuff. You can often reverse it (like melting ice back to water).
- A
chemical change means new substances are made — you can’t easily undo it. Signs include color change, bubbles, heat, light, or smoke.
Now let’s look at each one:
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1. Salt dissolved in water
When salt dissolves in water, it seems to disappear — but if you evaporate the water, the salt comes back. No new substance is made. It’s just mixed in.
→ This is a
physical change.
Evidence: You can get the salt back by boiling off the water. The salt didn’t turn into something else.
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2. Bread baking
When bread bakes, the dough rises, turns brown, and smells good. That’s because yeast makes gas (bubbles), and heat causes reactions that make new flavors and colors. You can’t unbake bread!
→ This is a
chemical change.
Evidence: Color change (golden brown), smell changes, texture changes permanently, and gases are produced (that’s why it rises).
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3. Sugar dissolved in water
Just like salt — sugar disappears when stirred in water, but if you let the water evaporate, sugar crystals come back. Nothing new was made.
→ This is a
physical change.
Evidence: You can recover the sugar by evaporation. No new substance formed.
---
4. Water boiling
Boiling water turns liquid water into steam (gas). But it’s still H₂O — just in a different form. If you cool the steam, it becomes water again.
→ This is a
physical change.
Evidence: Change of state only (liquid → gas). Reversible by cooling. No new substance created.
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5. Baking soda and vinegar
When you mix them, they fizz and bubble like crazy! That’s carbon dioxide gas being made. Also, the mixture gets colder sometimes. You can’t get the original baking soda and vinegar back easily.
→ This is a
chemical change.
Evidence: Gas production (bubbles), temperature change, and new substances formed (carbon dioxide, water, and sodium acetate).
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Final Answer:
| Physical or chemical change? | Evidence to support your conclusion |
|------------------------------|-------------------------------------|
| Salt dissolved in water | Physical – Salt can be recovered by evaporating water; no new substance formed. |
| Bread baking | Chemical – Color, smell, and texture change permanently; gases produced during rising. |
| Sugar dissolved in water | Physical – Sugar can be recovered by evaporation; no new substance formed. |
| Water boiling | Physical – Only change of state (liquid to gas); reversible by condensation. |
| Baking soda and vinegar | Chemical – Produces gas (bubbles), temperature change, and new substances formed. |
Parent Tip: Review the logic above to help your child master the concept of physical or chemical change worksheet.
