1. Do Now Please write HW in your agenda. Please update your table of contents. Please take the sheets from the front cart and place them in your notebook as indicated. Turn to your post-lab answers for discussion (page 114) Page #TitleDate 115Understanding Chemical Reactions2/9 116Evidence of Chemical Reactions2/9 117Chemical Equations2/9

2. Post-Lab Questions 1. What would you have expected to happen to the mass after the reaction if the balloon was not used? Explain why. 2. According to your results, what should be expected about the number of atoms present in your setup before and after this experiment?

3. Conservation of Mass

4. Evidence of Chemical Reactions - Change in Properties Change in color Formation of bubbles Change in odor Formation of a precipitate (solid)

5. Evidence of Chemical Reactions - Change in Energy Warming or coolingRelease of light

6. C + O 2  CO 2 Reactants are the starting substances in a chemical reaction. Reactants are written to the left of the arrow. The arrow is read as “yields” or “produces.” Products are the substances produced by the chemical reaction. Products are written to the right of the arrow. Chemical Equation

7. 2 H 2 + O 2  2 H 2 O Reactants are the starting substances in a chemical reaction, written to the left of the arrow. A subscript indicates the number of atoms of a particular element found in a molecule. The arrow is read as “yields” or “produces.” Products are the substances produced by the chemical reaction, written to the right of the arrow. A coefficient indicates the number of molecules. Chemical Equations

8. H 2 + O 2  H2OH2O 2 H 2 + O 2  2 H 2 O Counting Atoms

9. Chemical Equations 2 Mg + S 2  2 MgS

10. C 3 H 8 + 5O 2  3H 2 O + 3CO 2C =H = O = NaOH + H 2 SO 4  Na 2 SO 4 + H 2 ONa =O =H = S =