Across
- 4. to cause to fill or become covered with water, especially in a way that causes problems
- 5. a device that changes energy from the sun into electricity
- 7. gas, coal, and oil, that were formed underground from plant and animal remains millions of years ago
- 8. no longer existing
Down
- 1. to make an area or substance, usually air, water, or soil, dirty or harmful to people, animals, and plants, especially by adding harmful chemicals
- 2. a chemical element (= simple chemical substance), which exists in all plants and animals, and is an important part of coal and oil
- 3. a hard, black substance that is dug from the earth in pieces, and can be burned to produce heat or power
- 4. strong, unpleasant, and sometimes dangerous gas or smoke
- 6. an amount of a substance that is produced and sent out into the air that is harmful to the environment, especially carbon dioxide