Question

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

An ice cube melting in the sun and turning into water and then evaporating is a change of state (solid - liquid - gas). No new substance is formed. So it is a physical change (P).

Step2: Analyze chemical mixing producing gas

When two chemicals are mixed and a gas is produced, a new substance (the gas) is formed. So it is a chemical change (C).

Step3: Analyze bicycle rusting

Rusting of a bicycle is a chemical reaction between iron in the bicycle, oxygen, and water to form iron oxide (rust). A new substance is formed. So it is a chemical change (C).

Step4: Analyze crushing a solid to powder

Crushing a solid to powder only changes the physical form of the substance. No new substance is formed. So it is a physical change (P).

Step5: Analyze mixing substances producing light

When two substances are mixed and light is produced, a chemical reaction is likely occurring and new substances are formed. So it is a chemical change (C).

Step6: Analyze ice melting and reacting with sodium

The melting of ice is a physical change. But when it reacts with sodium, a chemical reaction occurs and new substances are formed. So overall it is a chemical change (C).

Step7: Analyze mixing salt and pepper

Mixing salt and pepper is just a physical combination of two substances. No new substance is formed. So it is a physical change (P).

Step8: Analyze dissolving chocolate syrup in milk

Dissolving chocolate syrup in milk is a physical process of dispersion. No new substance is formed. So it is a physical change (P).

Step9: Analyze toasting a marshmallow

Toasting a marshmallow over a camp - fire causes a chemical reaction due to heat, changing the composition of the marshmallow. A new substance is formed. So it is a chemical change (C).

Step10: Analyze cutting a marshmallow in half

Cutting a marshmallow in half only changes its physical shape. No new substance is formed. So it is 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