Question

the following changes are physical
1.
cutting an apple
2.
water changes to steam
3.
sugar dissolves in water
4.
cooking pancakes
5.
inflating a tire
6.
melting ice
7.
combining baking soda and vineg
8.
silver tarnishing
9.
alcohol evaporating
10.
milk sours
11.
food is digested
12.
crumpling a piece of paper
13.
an iron axe rusts
14.
snow freezes to ice
15.
paper towel absorbs water

Explanation:

To determine if a change is physical or chemical, we use the definitions:

• Physical change: Alters form/appearance of a substance, but not its chemical identity (no new substance formed).
• Chemical change: Results in a new substance (due to chemical reactions, like rusting, souring, combustion).

Step 1: Analyze each change

1. Cutting an apple: Only changes shape (no new substance) → Physical.
2. Water changes to steam: Phase change (liquid to gas, same substance \( \text{H}_2\text{O} \)) → Physical.
3. Sugar dissolves in water: Dissolution (sugar remains sugar, just dispersed) → Physical.
4. Cooking pancakes: Heat causes chemical reactions (browning, protein denaturation) → Chemical.
5. Inflating a tire: Air (gas) is added, no new substance → Physical.
6. Melting ice: Phase change (solid to liquid, same substance \( \text{H}_2\text{O} \)) → Physical.
7. Combining baking soda and vinegar: Reacts to form \( \text{CO}_2 \), \( \text{H}_2\text{O} \), and salt → Chemical.
8. Silver tarnishing: Silver reacts with sulfur (e.g., in air) to form silver sulfide (new substance) → Chemical.
9. Alcohol evaporating: Phase change (liquid to gas, same substance \( \text{C}_2\text{H}_5\text{OH} \)) → Physical.
10. Milk sours: Bacteria cause fermentation (lactic acid forms, new substance) → Chemical.
11. Food is digested: Enzymes break down food into new molecules (e.g., glucose) → Chemical.
12. Crumpling a piece of paper: Only changes shape (no new substance) → Physical.
13. An iron axe rusts: Iron reacts with \( \text{O}_2 \) and \( \text{H}_2\text{O} \) to form rust (new substance) → Chemical.
14. Snow freezes to ice: Phase change (solid to solid, same substance \( \text{H}_2\text{O} \)) → Physical.
15. Paper towel absorbs water: Water is absorbed (no new substance) → Physical.

Answer:

(label "Physical" or "Chemical" for each):

1. Physical
2. Physical
3. Physical
4. Chemical
5. Physical
6. Physical
7. Chemical
8. Chemical
9. Physical
10. Chemical
11. Chemical
12. Physical
13. Chemical
14. Physical
15. Physical