Across
- 1. energy sources a source of energy that has been widely used for many years.
- 4. energy source a source of energy that is not common as conventional sources alternative energy sources tend to be renewable and have few negative impacts on the environment.
- 5. energy balance the balance between the energy lost by the earth into space and the energy gained by solar radiation trapped by the earth's atmosphere.
- 7. gases such as water vapor, carbon dioxide, methane, and nitrous oxides that trap energy in the earth's atmosphere.
- 8. energy resource a source of energy that can be used indefinitely, without running out.
- 10. warming and increase in the earth's global temperature due to changes in the atmosphere that enhance the greenhouse effect.
- 12. energy source a source of energy that has been widely used for many years.
- 13. force-produced objects rub against each other.
- 14. solar heating caused by the passage of radiant energy through the windows of a building.
Down
- 2. energy resource a source of energy that could eventually be used up.
- 3. active solar energy system a device that harnesses radiant energy from the sun and converts it into a more useful form of energy.
- 6. fuels concentrated sources of chemical energy such as coal, oil, and natural gas that were formed deep in the earth's structure over millions of years from decayed and compressed plant and animal materials.
- 9. liquid fuel such as ethanol produced from plant or animal material.
- 10. effect a rise in temperature resulting from certain gases in the lower atmosphere trapping radiant energy and warming the earth's surface.
- 11. energy radiant energy (mostly visible light and infrared radiation) produced at the sun's outer surface and radiated out into space.