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 - chemical change definitions

Physical change involves size, shape, or state change with no new substance. Chemical change forms a new substance.

Step2: Analyze NaCl dissolving in water

NaCl dissolving in water is a physical change as it just disperses in water without forming a new substance. So it's P.

Step3: Analyze silver tarnishing

Silver tarnishing is a chemical change as silver reacts with sulfur - containing compounds in air to form silver sulfide (a new substance). So it's C.

Step4: Analyze an apple being cut

Cutting an apple is a physical change as it only changes the shape and size of the apple, no new substance is formed. So it's P.

Step5: Analyze water turning to steam

Heating water to steam is a physical change as it's a state change from liquid to gas without forming a new substance. So it's P.

Step6: Analyze baking - soda reacting with vinegar

Baking soda reacting with vinegar is a chemical change as carbon dioxide gas, water, and a salt are formed (new substances). So it's C.

Step7: Analyze iron rusting

Iron rusting is a chemical change as iron reacts with oxygen and water to form iron oxide (rust, a new substance). So it's C.

Step8: Analyze alcohol evaporating

Alcohol evaporating is a physical change as it changes from liquid to gas without forming a new substance. So it's P.

Step9: Analyze milk souring

Milk souring is a chemical change as bacteria ferment lactose in milk to form lactic acid (a new substance). So it's C.

Step10: Analyze sugar dissolving in water

Sugar dissolving in water is a physical change as it just disperses in water without forming a new substance. So it's P.

Step11: Analyze wood rotting

Wood rotting is a chemical change as microorganisms break down the complex organic compounds in wood into simpler substances (new substances). So it's C.

Step12: Analyze pancakes cooking

Pancakes cooking is a chemical change as the heat causes chemical reactions in the batter like the Maillard reaction, forming new substances with different flavors and textures. So it's C.

Step13: Analyze grass growing

Grass growing is a chemical change as photosynthesis and other biochemical processes occur to build new plant tissues (new substances). So it's C.

Step14: Analyze inflating a tire

Inflating a tire is a physical change as it just changes the volume of the tire by adding air, no new substance is formed. So it's P.

Step15: Analyze food digesting

Food digesting is a chemical change as enzymes break down large food molecules into smaller ones (new substances). So it's C.

Step16: Analyze paper towel absorbing water

Paper towel absorbing water is a physical change as it's just a capillary - action process without forming a new substance. So it's P.

Answer:

1. P
2. C
3. P
4. P
5. C
6. C
7. P
8. C
9. P
10. C
11. C
12. C
13. C
14. P
15. C
16. P