Question

part a physical and chemical changes can you recognize the chemical and physical changes that happen all around us? if you change the way something looks, but havent made a new substance, a physical change (p) has occurred. if the substance has been changes into another substance, a chemical change (c) has occurred. 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. two substances are mixed and light is produced. 6. a piece of ice melts and reacts with sodium. 7. mixing salt and pepper. 8. chocolate syrup is dissolved in milk. 9. a marshmallow is toasted over a campfire. 10. a marshmallow is cut in half.

Explanation:

Step1: Analyze ice - cube melting and evaporation

Ice cube melting to water and water evaporating is a change of state (solid - liquid - gas). No new substance is formed, so it's a physical change (P).

Step2: Analyze chemical mixing producing gas

When two chemicals mix and produce a gas, a new substance (the gas) is formed. This is a chemical change (C).

Step3: Analyze bicycle rusting

Rusting of a bicycle involves iron reacting with oxygen and water to form iron oxide (rust), a new substance. So it's a chemical change (C).

Step4: Analyze solid crushed to powder

Crushing a solid to powder only changes its physical form. No new substance is formed, so it's a physical change (P).

Step5: Analyze substances mixing and producing light

Producing light during a mixture usually indicates a chemical reaction that releases energy in the form of light. A new substance or substances are likely formed, so it's a chemical change (C).

Step6: Analyze ice - sodium reaction

Ice melting is a physical change, but when water reacts with sodium, new substances (such as sodium hydroxide and hydrogen gas) are formed. So overall it's a chemical change (C).

Step7: Analyze salt - pepper mixing

Mixing salt and pepper is a physical combination. No chemical reaction occurs, and no new substances are formed, so it's a physical change (P).

Step8: Analyze chocolate - syrup dissolving in milk

Dissolving chocolate syrup in milk is a physical process of dispersion. No new substances are formed, so it's a physical change (P).

Step9: Analyze marshmallow toasting

Toasting a marshmallow over a camp - fire causes a chemical reaction due to heat, changing the marshmallow's chemical composition. So it's a chemical change (C).

Step10: Analyze marshmallow cutting

Cutting a marshmallow only changes its physical shape. No new substance is formed, so it's a physical change (P).

Answer:

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