Question

physical and chemical changes
understanding main ideas
check the type of change or changes that apply to each description.
description physical change chemical change

1. occurs when energy is added or removed
2. a new substance is produced.
3. a substance changes form, but it remains the same substance.
4. freezing water is an example.

answer the following on a separate sheet of paper.

1. compare the total amount of energy before and after physical and chemical changes.
2. can energy be released during a chemical reaction? can it be absorbed? can a chemical reaction take place in which energy is neither absorbed or released?

building vocabulary
from the list below, choose the term that best completes each sentence. chemical energy melting law of conservation of energy sublimation thermal energy freezing vaporization chemical reaction evaporation boiling condensation

1. the higher the temperature of something, the greater its _.
2. the change in state from gas to liquid is called _.
3. energy that comes from bonds within matter is called _.
4. the change in state from liquid to gas is called _.
5. gas bubbles forming throughout the liquid is called _.
6. liquid changing to gas only at the surface is called _.
7. the change in state from solid to liquid is called _.
8. the change in state from liquid to solid is called _.
9. the _ states that during any change, the amount of energy stays the same.
10. another term for a chemical change is a(n) _.
11. in _, particles pass directly from solid to gas.

Explanation:

1. Physical changes can occur with energy addition/removal. Chemical changes also involve energy, but this is a general physical - change characteristic.
2. Production of a new substance is a chemical change.
3. A substance changing form but remaining the same is a physical change.
4. Freezing water is a physical change as only the state changes.
5. In physical and chemical changes, the total amount of energy is conserved according to the law of conservation of energy.
6. Energy can be released (exothermic) or absorbed (endothermic) in chemical reactions. A reaction with no energy change is very rare but theoretically possible under specific conditions.
7. Higher temperature means more thermal energy.
8. Gas - to - liquid change is condensation.
9. Energy from matter bonds is chemical energy.
10. Liquid - to - gas change is vaporization.
11. Gas bubbles forming throughout liquid is boiling.
12. Liquid changing to gas only at the surface is evaporation.
13. Solid - to - liquid change is melting.
14. Liquid - to - solid change is freezing.
15. The law of conservation of energy states energy amount stays the same during changes.
16. Another term for chemical change is chemical reaction.
17. Particles passing directly from solid to gas is sublimation.

Answer:

1. Physical Change
2. Chemical Change
3. Physical Change
4. Physical Change
5. The total amount of energy is conserved in both physical and chemical changes according to the law of conservation of energy.
6. Energy can be released (exothermic reactions) and absorbed (endothermic reactions) in chemical reactions. A chemical reaction with no energy absorption or release is very rare but theoretically possible.
7. thermal energy
8. condensation
9. chemical energy
10. vaporization
11. boiling
12. evaporation
13. melting
14. freezing
15. law of conservation of energy
16. chemical reaction
17. sublimation