Science

3. - The smallest unit of a chemical compound.
4. - A substance formed from two or more elements chemically united in fixed proportions.
6. - The basic unit of a chemical element.
7. - The force that attracts a body towards the center of the earth.
9. - The bouncing back of light from a surface.
13. - A protein that speeds up chemical reactions in the body.
14. - A substance that cannot be broken down into simpler substances.
15. - The powerhouse of the cell.

1. - The force exerted by magnets.
2. - Relating to or consisting of living cells.
5. - The process by which green plants make their own food.
8. - A process in which substances interact to form new substances.
10. - The flow of electric charge.
11. - The movement of water molecules through a semi-permeable membrane.
12. - The resistance of any physical object to a change in its state of motion.