Let's solve the worksheet by identifying each process as either a
physical change (P) or a
chemical change (C) based on the definitions provided:
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🔹 Definitions Recap:
-
Physical Change (P):
- A change in size, shape, or state.
- No new substance is formed.
-
Chemical Change (C):
- A change in physical and chemical properties.
- A new substance is formed.
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Now, let’s go through each item:
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1. NaCl (Table Salt) dissolves in water.
✔ P – Dissolving is a physical change. The salt ions are dispersed in water, but no new substance is formed. It can be reversed by evaporation.
2. Ag (Silver) tarnishes.
✔ C – Tarnishing is a chemical reaction with sulfur in the air forming silver sulfide (a new substance).
3. An apple is cut.
✔ P – Cutting changes the size and shape, but no new substance is formed.
4. Heat changes H₂O to steam.
✔ P – This is a phase change (liquid → gas), no new substance forms.
5. Baking soda reacts to vinegar.
✔ C – This is a classic chemical reaction producing carbon dioxide gas, water, and sodium acetate. New substances form.
6. Fe (Iron) rusts.
✔ C – Rusting is an oxidation reaction forming iron oxide (a new substance).
7. Alcohol evaporates.
✔ P – Evaporation is a physical change from liquid to gas; no new substance.
8. Ice melts.
✔ P – Melting is a phase change (solid → liquid); still H₂O.
9. Milk sours.
✔ C – Souring involves bacterial action producing lactic acid — a new substance.
10. Sugar dissolves in water.
✔ P – Dissolving sugar is physical; it can be recovered by evaporation.
11. Wood rots.
✔ C – Rotting involves decomposition by fungi/microbes, creating new substances.
12. Pancakes cook.
✔ C – Cooking involves browning (Maillard reaction), which creates new compounds.
13. Grass grows.
✔ C – Growth involves photosynthesis and metabolic processes forming new organic molecules.
14. A tire is inflated.
✔ P – Air is compressed into the tire; no chemical change occurs.
15. Food is digested.
✔ C – Digestion breaks down food into simpler substances via chemical reactions (enzymes, acids).
16. Paper towel absorbs water.
✔ P – Absorption is a physical process; water is held in fibers, no new substance.
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✔ Final Answers:
1.
P
2.
C
3.
P
4.
P
5.
C
6.
C
7.
P
8.
P
9.
C
10.
P
11.
C
12.
C
13.
C
14.
P
15.
C
16.
P
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📝 Summary:
-
Physical Changes (P): 1, 3, 4, 7, 8, 10, 14, 16
-
Chemical Changes (C): 2, 5, 6, 9, 11, 12, 13, 15
This classification helps us understand whether a process alters the fundamental composition of matter (chemical) or just its form (physical).
Parent Tip: Review the logic above to help your child master the concept of chemical properties worksheet.
