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1. Stored energy is called p-------- energy. Movement energy is called k------ energy. (lesson 21a)
2. What can you say about the amount of energy before and after an energy transfer? (21a)
3. A battery transfers 10 J of energy to a motor, but 4 J of energy are wasted. What is the efficiency? (21a)
4. Where does most of the Earth's energy come from? (21b)
5. Plants use the Sun's energy to make their food in a process called p-------------. (21b)
6. The Sun's energy is called ----- energy. (21b)
7. What is biomass? (21b)
8. About how long has it taken for coal and oil to form? (21c)
9. Coal, oil and gas are non-renewable resources. What does this mean? (21c)
10. Name another non-renewable resource? (21c)
11. What fuel is 'burned' in your cells to release energy in respiration? (21d)
12. What gas do fuels need to burn? (21d)
13. What is formed during respiration? (21d)
14. What do we call our energy sources that will not run out? (21e)
15. Which source of energy comes from deep inside the Earth? (21e)

ANSWERS

1. Potential, kinetic.
2. It is the same.
3. 60%
4. the Sun.
5. Photosynthesis.
6. Solar.
7. Material from plants and animals.
8. Millions of years (about 300 million for coal.)
9. Once they are used up, they are gone forever.
10. Uranium.
11. Sugar (from your food).
12. Oxygen.
13. Carbon dioxide and water (plus energy).
14. Renewable.
15. Geothermal.