Question

instructions: classify each of the following changes in matter as physical p or chemical c.

1. grinding chalk into powder
2. dissolving salt in water
3. dissolving zinc in acid
4. tearing a piece of paper
5. stretching copper into wire
6. burning gasoline
7. hammering gold into foil
8. melting ice
9. digesting food
10. making hydrogen from water

Explanation:

To solve this, we determine if a change is physical (no new substance, just state/shape) or chemical (new substance formed).

31. Grinding chalk into powder

• Explanation: Only shape changes, no new substance.
• Answer: P

32. Dissolving salt in water

• Explanation: Salt dissolves, no new substance (can be reversed).
• Answer: P

33. Dissolving zinc in acid

• Explanation: Zinc reacts with acid, new substances (e.g., gas) form.
• Answer: C

34. Tearing a piece of paper

• Explanation: Only shape changes, no new substance.
• Answer: P

35. Stretching copper into wire

• Explanation: Only shape (physical form) changes, no new substance.
• Answer: P

36. Burning gasoline

• Explanation: Gasoline burns, forming CO₂, H₂O, etc. (new substances).
• Answer: C

37. Hammering gold into foil

• Explanation: Only shape (malleability) changes, no new substance.
• Answer: P

38. Melting ice

• Explanation: Ice (solid H₂O) becomes liquid H₂O—state change, no new substance.
• Answer: P

39. Digesting food

• Explanation: Food breaks down into new substances (e.g., nutrients) via reactions.
• Answer: C

40. Making hydrogen from water

• Explanation: Water (H₂O) splits into H₂ and O₂ (new substances).
• Answer: C

Final Answers (each line corresponds to the question number):

1. P
2. P
3. C
4. P
5. P
6. C
7. P
8. P
9. C
10. C

Answer:

To solve this, we determine if a change is physical (no new substance, just state/shape) or chemical (new substance formed).

31. Grinding chalk into powder

• Explanation: Only shape changes, no new substance.
• Answer: P

32. Dissolving salt in water

• Explanation: Salt dissolves, no new substance (can be reversed).
• Answer: P

33. Dissolving zinc in acid

• Explanation: Zinc reacts with acid, new substances (e.g., gas) form.
• Answer: C

34. Tearing a piece of paper

• Explanation: Only shape changes, no new substance.
• Answer: P

35. Stretching copper into wire

• Explanation: Only shape (physical form) changes, no new substance.
• Answer: P

36. Burning gasoline

• Explanation: Gasoline burns, forming CO₂, H₂O, etc. (new substances).
• Answer: C

37. Hammering gold into foil

• Explanation: Only shape (malleability) changes, no new substance.
• Answer: P

38. Melting ice

• Explanation: Ice (solid H₂O) becomes liquid H₂O—state change, no new substance.
• Answer: P

39. Digesting food

• Explanation: Food breaks down into new substances (e.g., nutrients) via reactions.
• Answer: C

40. Making hydrogen from water

• Explanation: Water (H₂O) splits into H₂ and O₂ (new substances).
• Answer: C

Final Answers (each line corresponds to the question number):

1. P
2. P
3. C
4. P
5. P
6. C
7. P
8. P
9. C
10. C