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.
-
Chemical Change: A change in which
new substances are formed due to a chemical reaction. The original substance is transformed into one or more different substances.
- Examples: rusting, burning, digestion.
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Now let’s analyze each item:
1)
Melting of an ice cube
→ Ice turns into water (solid → liquid), but it's still H₂O.
✔ Physical change
2)
Rusting of an iron nail
→ Iron reacts with oxygen to form iron oxide (rust). New substance formed.
✔ 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
→ Size changes, but paper is still paper. No new substance.
✔ Physical change
5)
Boiling water
→ Water changes 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
→ Shape changes, but the material is still glass. No new substance.
✔ Physical change
8)
Tarnishing of silver
→ Silver reacts with sulfur in air to form silver sulfide (black tarnish). New compound forms.
✔ Chemical change
9)
Dissolving sugar in water
→ Sugar molecules disperse in water, but no chemical reaction occurs. Sugar 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
→ Liquid water becomes solid ice; still H₂O.
✔ Physical change
12)
Crushing a can
→ Shape changes, but aluminum remains aluminum.
✔ Physical change
13)
Digesting food in your stomach
→ Food is broken down into simpler molecules (e.g., proteins into amino acids) via enzymes. Chemical bonds are broken.
✔ Chemical change
14)
Ripping a piece of cloth
→ Cloth is torn into smaller pieces. Material unchanged.
✔ Physical change
15)
Combining hydrogen and oxygen to form water
→ H₂ + O₂ → H₂O. This is a combustion reaction forming a new substance.
✔ 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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This worksheet helps students understand that
physical changes involve changes in state or shape without altering the substance’s identity, while
chemical changes result in new substances with different properties.
Parent Tip: Review the logic above to help your child master the concept of chemical changes worksheet.
