Earth Hour

3. Energy produced by splitting or joining the center of small particles called atoms
4. Stored energy, such as the still water sitting behind a dam, ready to fall
7. Energy produced by movement of charged particles
8. Energy from the heat
12. A resource that cannot be depleted
13. Practices that can be continued indefinitely, with minimal harm to the natural environment, such as the use of renewable resources
14. The vibrations of molecules as sound waves travel
15. Materials that are extracted from the earth, such as coal, oil or natural gas
16. A resource that can be depleted, such as fossil fuels
17. A gas that is the main ingredient of both natural gas and biogas
19. Energy of motion, water that is flowing over a dam
20. Stored energy that can be released through chemical reaction, found in things like food and batteries

1. Energy generated by moving water
2. Heat energy from inside the earth
5. Contamination of the natural environment with the harmful substances such as consequence of human activities; a byproduct of many energy sources
6. Things that are alive, such as plant material or animal watse that can be used to make biogas
9. The ability to do work
10. The category of energy that includes solar and light energy
11. Energy from the sun's rays
18. Output compared to input. If a device does as much work for us as energy we put into it