2.  A chemical formula tells you which elements are in a compound and how many atoms of each element there are.  For example: C 6 H 12 O 6 There are 6 carbons,12 hydrogens and 6 Oxygen in this molecule

3. Reactions have:  Reactants – starting chemicals  Products – ending chemicals  In a chemical equation the arrow point from the reactants to the products 2 H 2 O 2 ---> 2 H 2 O + O 2 Photosynthesis Respiration

4.  Nothing is created or destroyed in a chemical reaction.  All the atoms of an element in the reactants will be in the products  Bonds are broken and formed in the rearrangement of the atoms.

5.  Ability to work or cause change.  Energy is never lost, it only changes form.  Different forms of energy. ChemicalThermalMechanicalelectrical

6.  Reactions that absorb energy are endothermic.  Example: making glucose.  Exothermic: Reactions that release energy  Example: breaking down glucose

7.  Activation energy is needed to start the chemical reaction.  Catalysts reduce the amount of activation needed. Activation energy Think: why is it important for a cell to reduce the amount of energy needed to start a reaction?

8.  Don’t Panic!  This is a fancy way to talk about electron transfers between products and reactants  Oxidation: A substance gives up an electron and becomes more positive  Reduction: A substance gains an electron and becomes more negative

9. 1. What are reactants and products? 2. Write out the following in words:H 2 SO 4 3. How will knowing what ‘endo’,‘ex’, and ‘therm’ mean help you in remembering what happens in endothermic and exothermic reactions? 4. What is activation energy? 5. What is a catalyst?