Question

physical and chemical properties and changes
directions: answer the following questions on the front and back of this paper.

physical property

1. observed with senses
2. determined without destroying matter

chemical property

1. indicates how a substance reacts with something else
2. matter will be changed into a new substance after the reaction

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. alka seltzer in water
_____6. fe (iron) rusts.
_____7. alcohol evaporates .
_____8. ice melts.
_____9. a cake is done baking.
_____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.

physical and chemical changes
decide whether a physical or chemical change has occurred and give evidence for your decision. if additional space is needed write on your paper.

1. an ice cube is placed in the sun. later there is a puddle of water. later still the puddle is gone.
2. two chemical are mixed together and a gas is produce.
3. a bicycle changes color as it rusts.
4. a solid is crushed to a powder.
5. a piece of wood is burning.
6. a piece of calcium reacts with sodium to form table salt.
7. mixing salt and pepper.
8. clothes were bleached to remove the dirt and grass stains.
9. a marshmallow is toasted over a campfire.
10. the air freshener made the room smell fresh.

Answer:

Part 1: Identify as Physical (P) or Chemical (C) Changes

1. NaCl (Table Salt) dissolves in water

• Explanation: Dissolving salt in water is a physical change (no new substance, just dispersion).
• Answer: P

1. Ag (Silver) tarnishes

• Explanation: Tarnishing involves a reaction with sulfur/oxygen (new substance, silver sulfide).
• Answer: C

1. An apple is cut

• Explanation: Cutting changes shape/size, no new substance.
• Answer: P

1. Heat changes H₂O to steam

• Explanation: Phase change (liquid to gas), no new substance.
• Answer: P

1. Alka Seltzer in water

• Explanation: Reacts to produce gas (new substance, e.g., CO₂).
• Answer: C

1. Fe (Iron) rusts

• Explanation: Rust (Fe₂O₃) is a new substance from reaction with O₂/H₂O.
• Answer: C

1. Alcohol evaporates

• Explanation: Phase change (liquid to gas), no new substance.
• Answer: P

1. Ice melts

• Explanation: Phase change (solid to liquid), no new substance.
• Answer: P

1. A cake is done baking

• Explanation: Baking involves chemical reactions (e.g., protein denaturation, Maillard reaction).
• Answer: C

1. Sugar dissolves in water

• Explanation: Dissolving is a physical change (no new substance, just dispersion).
• Answer: P

1. Wood rots

• Explanation: Rotting is decomposition (new substances, e.g., fungi, CO₂).
• Answer: C

1. Pancakes cook

• Explanation: Cooking involves chemical reactions (e.g., protein denaturation, Maillard reaction).
• Answer: C

1. Grass grows

• Explanation: Growth involves photosynthesis (new substances, e.g., glucose).
• Answer: C

1. A tire is inflated

• Explanation: Inflation changes shape/size, no new substance.
• Answer: P

1. Food is digested

• Explanation: Digestion breaks food into new substances (e.g., glucose, amino acids).
• Answer: C

1. Paper towel absorbs water

• Explanation: Absorption is a physical process (no new substance, just water uptake).
• Answer: P

Part 2: Decide Physical/Chemical Change & Evidence

1. An ice cube in the sun (melts to water, then evaporates)

• Change: Physical
• Evidence: Phase changes (solid→liquid→gas); no new substance (still H₂O).

1. Two chemicals mixed, gas produced

• Change: Chemical
• Evidence: Gas production (sign of reaction); new substance formed.

1. Bicycle rusts (changes color)

• Change: Chemical
• Evidence: Rust (Fe₂O₃) is a new substance; color change (sign of reaction).

1. Solid crushed to powder

• Change: Physical
• Evidence: Change in size/shape; no new substance.

1. Wood burning

• Change: Chemical
• Evidence: Burning produces ash, CO₂ (new substances); heat/light (signs of reaction).

1. Calcium + sodium → table salt

• Change: Chemical
• Evidence: New substance (table salt, NaCl) formed from reaction.

1. Mixing salt and pepper

• Change: Physical
• Evidence: No reaction; mixture of two substances (no new substance).

1. Clothes bleached (remove stains)

• Change: Chemical
• Evidence: Bleach reacts with stains (new substances formed to remove color).

1. Marshmallow toasted

• Change: Chemical
• Evidence: Toasting causes Maillard reaction (new substances, color/ flavor change).

1. Air freshener makes room smell fresh

• Change: Physical
• Evidence: Scent dispersion (no new substance; just molecules spreading).

Final Answers (Part 1)

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

(Part 2 answers are summarized in the explanations above.)