2. A chemical reaction in which a compound is broken down (decomposed) into simpler substances

3. A reaction in which the composition of a substance is changed

4. Number placed in front of a formula to show how many moles of that substance

5. Chemical reaction in which a compound is broken down into simpler substances (analysis) AB  A + B

6. Molecule containing two identical atoms

7. Chemical reaction in which ions exchange places AB + CD  AD + BD

8. Chemical formula with coefficients in lowest terms

9. Chemical reaction that absorbs heat Heat is on the reactant (left) side of the equation Products have higher potential energy than reactants

10. Chemical reaction that releases heat Heat is on the product (right) side of the equation Products have less potential energy than reactants

11. Symbols and subscripts that represent the composition of a substance

12. Actual ratio of atoms in a substance (not necessarily lowest terms)

13. Smallest unit of a covalently bonded substance

14. Change that does not alter the chemical properties of a substance

15. Covalently bonded group of atoms that have a net charge and behave as a single unit

16. Substance formed in a chemical reaction On the right side of the equation

17. Information that cannot be counted or measured

18. Information that can be counted or measured

19. Starting substance in a reaction On the left side of the equation

20. Reaction in which a more reactive element replaces a less reactive element in a compound AB + C  AC + B

21. Number written after a symbol that tells how many of that substance

22. A one, two, or three (experimental only), letter designation of an element

23. Chemical reaction in which two or more substances chemically combine to form one substance A + B  AB

25. Sum of atomic masses of all atoms

26. Formula mass expressed in g rather than in u

27. 6.02 x 10 23 particles Number atoms present on 12.000g of carbon-12

28. Percent of each element compared to the total mass of the compound