1. Chemical Formulas & Equations

2. Molecule A combination of two or more atoms bonded together.

3. Compound A substance made of two or more different elements that are chemically combined. Involves the sharing, stealing, or giving up of valence electrons H 2 O Water is a compound

4. Subscript A number in a chemical formula that shows how many atoms of each element are present. Example: The “two” in H 2 O

5. Coefficient A number in front of a chemical formula showing how many molecules or atoms are present. Example: The “three” in 3H 2 O The “two” in 2Fe

6. Chemical Formula A combination of symbols and numbers that show how many atoms of each element are present in a molecule Example: H 2 SO 4 One molecule of sulfuric acid has two atoms of hydrogen, one atom of sulfur, and 4 atoms of oxygen

7. Chemical Equation An easy way to show a chemical reaction using symbols instead of words. 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 It reads like this…….. 6 molecules of carbon dioxide react with 6 molecules of water to yield 1 molecule of glucose and 6 molecules of oxygen

8. Reactants A substance present at the start of a chemical reaction Products Substance that is formed as the result of a chemical reaction 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 ReactantsProducts *The red arrow means “Yields”

9. The Law of Conservation of Mass Matter can not be created or destroyed. Chemical equations must be balanced. This is done by changing the coefficients (not the subscripts!) Not balanced: H 2 + O 2 H 2 O Balanced: 2H 2 + O 2 2H 2 O