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Across 1. allow living things to grow, develop, reproduce, and adapt 6. reactants that bond to enzymes 7. number written infront of a reactant, or product 9. pure substances made up of only one kind of atom 11. force that holds compounds together 14. charged atom, has lost or gained electrons 16. forms of the same element with different numbers of neutrons 18. number and type of atoms are the same on both sides of a chemical equation 20. chemical bond formed when electrons are shared 21. uncharged charged particle of an atom 22. building blocks of matter 23. reduces the amount of energy needed for a chemical reaction to take place 24. specific location substrates bond to enzymes

Down 2. compound in which atoms are held together by covalent bonds 3. minimum amount of energy needed for a reaction to take place 4. Isotopes that give off radiation 5. starting substances in a chemical reaction (left side of arrow) 8. biological catalysts (speeds up chemical reactions in living things) 10. positively charged particle of an atom 12. symbolic representation of a chemical reaction 13. chemical bond formed by gaining and loseing electrons 15. force that holds molecules together 17. negatively charged particle of an atom 19. substances formed in a reaction (right side of arrow) 20. substances with unique properties that are formed when elements combine 21. center of an atom