Let's go through each of the 15 changes listed in the worksheet and determine whether each is a
physical change or a
chemical change. Here's how we can distinguish between them:
🔬 Definitions:
-
Physical Change: A change in which the substance’s form or state changes, but
no new substances are formed. The chemical composition remains the same.
- Examples: Melting, freezing, cutting, dissolving, crushing.
-
Chemical Change: A change in which
new substances are formed due to a chemical reaction. There is a change in the chemical composition.
- Examples: Rusting, burning, digestion, tarnishing.
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Now let’s analyze each item:
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1)
Melting of an ice cube
→ The ice turns into water, but it's still H₂O. No new substance.
✔ Physical Change
2)
Rusting of an iron nail
→ Iron reacts with oxygen and water to form rust (iron oxide), a new substance.
✔ Chemical Change
3)
Burning of a piece of paper
→ Paper combusts, producing ash, smoke, and gases. New substances are formed.
✔ Chemical Change
4)
Cutting a piece of paper
→ The paper is just divided into smaller pieces; no new substance.
✔ Physical Change
5)
Boiling water
→ Water turns from liquid to gas (steam), but it's still H₂O.
✔ Physical Change
6)
Baking a cake
→ Ingredients undergo chemical reactions (e.g., proteins denature, sugars caramelize). New substances form.
✔ Chemical Change
7)
Breaking a glass
→ The glass is shattered, but it's still glass. No new substance.
✔ Physical Change
8)
Tarnishing of silver
→ Silver reacts with sulfur in the air to form silver sulfide (black coating). New substance.
✔ Chemical Change
9)
Dissolving sugar in water
→ Sugar molecules disperse in water, but they don’t chemically change. Can be recovered by evaporation.
✔ Physical Change
10)
Mixing baking soda and vinegar
→ Produces carbon dioxide gas, water, and sodium acetate. Bubbles form — evidence of a chemical reaction.
✔ Chemical Change
11)
Freezing water into ice cubes
→ State change from liquid to solid. Still H₂O.
✔ Physical Change
12)
Crushing a can
→ Shape changes, but aluminum remains aluminum. No new substance.
✔ Physical Change
13)
Digesting food in your stomach
→ Food is broken down into simpler molecules via enzymes and acids. New substances (nutrients) are formed.
✔ Chemical Change
14)
Ripping a piece of cloth
→ The fabric is torn, but the material remains the same. No chemical change.
✔ Physical Change
15)
Combining hydrogen and oxygen to form water
→ This is a classic chemical reaction: 2H₂ + O₂ → 2H₂O. A new compound forms.
✔ Chemical Change
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✔ Final Answers:
1) Physical
2) Chemical
3) Chemical
4) Physical
5) Physical
6) Chemical
7) Physical
8) Chemical
9) Physical
10) Chemical
11) Physical
12) Physical
13) Chemical
14) Physical
15) Chemical
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Parent Tip: Review the logic above to help your child master the concept of physical and chemical change worksheet.
