Science Crossword

3. cloudy mixture in which tiny particles of one substance are held within another and particles cannot be separated out from the other substance
4. chemical reaction that releases energy
7. catalyst involved in chemical reactions in living things
8. group 2 elements in the periodic table; their reactivity is not as strong as that of the alkali metals
10. slow chemical change that occurs when oxygen in the air reacts with a metal
12. change that results when two or more substances react to create a different substance or substances
13. a reaction that takes place when two or more substances react to form new substances
15. atom that has become electrically charged because it has lost or gained electrons
16. invisible negatively charged particle that orbits the nucleus of an atom
17. chemical combination of two or more elements in a specific ratio
18. pure substance that cannot be broken down into other substances
20. an experiment in which all reactants and all products of a chemical reaction are accounted for
21. the most reactive non-metals
22. chemical reaction that occurs when oxygen reacts with a substance to form a new substance and give off energy
23. mass of one atom of an element calculated from the total number of protons, neutrons, and electrons of that atom
24. vertical column of elements in the periodic table that have similar chemical properties

1. combination of symbols that represent a compound
2. orbit of electrons around the nucleus of an atom
5. chemical reaction that absorbs energy
6. the mass of the products always equals the mass of the reactants
9. energy stored in chemicals and released when chemicals react
10. substance that helps a chemical reaction to proceed more quickly
11. number of protons in the nucleus of one atom of an element
14. compound that dissolves in water to form a solution with a pH lower than 7
19. group 1 elements in the periodic table, not including hydrogen; the most reactive of the metals