A chemical formula tells you which elements are in a compound and how many atoms of each element there are.

For example:C6H12O6

There are 6 carbons,12 hydrogens and 6 Oxygen in this molecule

Reactions have:Reactions have: ReactantsReactants – starting chemicals – starting chemicals ProductsProducts – ending chemicals – ending chemicals In a chemical equation the In a chemical equation the

arrow points from the arrow points from the reactants to the products reactants to the products

2 H2 H22OO22 ---> 2 H ---> 2 H22O + OO + O22

PhotosynthesisPhotosynthesis

Respiration Respiration

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.

Ability to work or cause Ability to work or cause change.change.

Energy is never Energy is never created or lost, it only created or lost, it only changes form.changes form.

Different forms of Different forms of energy.energy. ChemicalChemical ThermalThermal MechanicalMechanical electrical electrical

Reactions that absorb energy are Reactions that absorb energy are endothermic/ endergonic endothermic/ endergonic Example: making glucose.Example: making glucose.

Exothermic/ exergonic: Reactions that Exothermic/ exergonic: Reactions that release energyrelease energy Example: breaking down glucoseExample: breaking down glucose

Activation energy is Activation energy is needed to start the needed to start the chemical reaction.chemical reaction.

Catalysts reduce Catalysts reduce the amount of the amount of activation needed.activation needed.

Activation energyActivation energy

Think: Why is it important for a cell to reduce the amount of energy needed to start a reaction?

Don’t Panic!Don’t Panic! This is a fancy way to talk about electron This is a fancy way to talk about electron

transfers between products and reactantstransfers between products and reactants OxidationOxidation: A substance gives up an : A substance gives up an

electron and becomes more electron and becomes more positivepositive ReductionReduction: A substance gains an electron : A substance gains an electron

and becomes more and becomes more negativenegative

1. What are reactants and products?2. Write out the following in words:H2SO4

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?