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 its chemical composition remains the same. No new substances are formed.
-
Chemical Change: A change in which one or more new substances are formed due to a chemical reaction. The molecular structure changes.
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Now, let's analyze each item:
1)
Melting of an ice cube
→ The solid ice turns into liquid water, but it's still H₂O.
✔ Physical Change
2)
Rusting of an iron nail
→ Iron reacts with oxygen to form iron oxide (rust). New substance is formed.
✔ Chemical Change
3)
Burning of a piece of paper
→ Paper combusts, producing ash, smoke, and gases. New substances form.
✔ Chemical Change
4)
Cutting a piece of paper
→ Only size changes; no new substance is created.
✔ 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 stays the same.
✔ Physical Change
8)
Tarnishing of silver
→ Silver reacts with sulfur in the air to form silver sulfide (dark tarnish). New substance forms.
✔ Chemical Change
9)
Dissolving sugar in water
→ Sugar molecules disperse in water, but no chemical reaction occurs. Can be reversed 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.
✔ Physical Change
13)
Digesting food in your stomach
→ Food is broken down into simpler molecules via enzymes (e.g., proteins → amino acids). Chemical reactions occur.
✔ Chemical Change
14)
Ripping a piece of cloth
→ Size and shape change, but fabric composition unchanged.
✔ Physical Change
15)
Combining hydrogen and oxygen to form water
→ This is a classic chemical reaction: 2H₂ + O₂ → 2H₂O. New substance formed.
✔ 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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Let me know if you'd like this as a printable answer key!
Parent Tip: Review the logic above to help your child master the concept of physical change and chemical change worksheet.
