| 1. |
The invisible mixture of gases we breathe.
air |
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| 2. |
A plant with leaves, roots, and a single, woody trunk.
_________________ |
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| 3. |
A person who helps or offers to do something without getting paid.
_________________ |
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| 4. |
Something involving risk or danger.
_________________ |
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| 5. |
This is the third planet from the sun.
_________________ |
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| 6. |
To throw garbage on the ground instead of in a garbage can.
_________________ |
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| 7. |
The process by which plant cells use light, water, and carbon dioxide to make food.
_________________ |
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| 8. |
The protection and more efficient use of natural resources.
_________________ |
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| 9. |
This occurs when running water, sea waves, wind, or glaciers pick up and carry away materials from the earth's surface.
_________________ |
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| 10. |
The large body of saltwater that covers about 70% of the earth's surface.
_________________ |
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| 11. |
A form of energy that is used in homes and is produced by the movement of electrons.
_________________ |
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| 12. |
A layer in the atmosphere which blocks many of the sun's ultraviolet rays from reaching the earth.
_________________ |
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| 13. |
A place where garbage is buried.
_________________ |
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| 14. |
The amount of work a machine does compared to the amount of energy needed to run the machine.
_________________ |
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| 15. |
To remove dirt or stains from something.
_________________ |
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| 16. |
A type of fuel used in cars with internal-combustion engines. This is made from petroleum.
_________________ |
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| 17. |
The place or type of environment where an animal or plant naturally lives or grows.
_________________ |
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| 18. |
A metal container.
_________________ |
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| 19. |
This type of precipitation is caused by pollution and is harmful to plants, animals, bodies of water, and buildings.
_________________ |
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| 20. |
The apparent rise in the earth's temperature that scientists believe is caused by an increase in the amount of carbon dioxide and other gases in the air.
_________________ |
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| 21. |
A living creature that can breathe and move about.
_________________ |
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| 22. |
A solid, hard black mineral that burns and gives off heat. It's formed from partly decayed vegetable matter that's under great pressure and heat in the earth.
_________________ |
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