Question

physical change 1. a change in size, shape, or state 2. no new substance is formed chemical change 1. a change in the physical and chemical properties 2. a new substance is formed identify the following as physical (p) or chemical (c) changes. 1. nacl (table salt) dissolves in water. 2. ag (silver) tarnishes. 3. an apple is cut. 4. heat changes h₂o to steam. 5. baking soda reacts to vinger. 6. fe (iron) rusts. 7. alcohol evaporates. 8. ice melts. 9. milk sours. 10. sugar dissolves in water. 11. wood rots. 12. pancakes cook. 13. grass grows. 14. a tire is inflated. 15. food is digested. 16. paper towel absorbs water.

Explanation:

Step1: Recall physical - change criteria

Physical change: change in size, shape, state; no new substance formed. Chemical change: change in physical and chemical properties; new substance formed.

Step2: Analyze each case

1. NaCl dissolves in water. No new substance, just a mixture. So it's a physical change (P).
2. Ag tarnishes. Silver reacts with sulfur - containing substances in air to form silver sulfide. New substance, so it's a chemical change (C).
3. An apple is cut. Just a change in shape, no new substance. Physical change (P).
4. Heat changes H₂O to steam. Change in state, no new substance. Physical change (P).
5. Baking soda reacts to vinegar. Produces carbon dioxide and other substances. Chemical change (C).
6. Fe rusts. Iron reacts with oxygen and water to form iron oxide. Chemical change (C).
7. Alcohol evaporates. Change in state, no new substance. Physical change (P).
8. Ice melts. Change in state, no new substance. Physical change (P).
9. Milk sours. Micro - organisms cause chemical reactions to form new substances. Chemical change (C).
10. Sugar dissolves in water. No new substance, just a mixture. Physical change (P).
11. Wood rots. Micro - organisms break down wood into new substances. Chemical change (C).
12. Pancakes cook. Chemical reactions occur during cooking, new substances are formed. Chemical change (C).
13. Grass grows. Many chemical reactions occur during growth. Chemical change (C).
14. A tire is inflated. Change in size, no new substance. Physical change (P).
15. Food is digested. Chemical reactions break down food into new substances. Chemical change (C).
16. Paper towel absorbs water. No new substance, just a physical absorption. Physical change (P).

Answer:

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