1. Chemical reaction
   1. chemical change
   2. one or more new substances produced
   3. different to physical change
      1. dissolving
      2. sugar in water
      3. evaporation
         1. change of energy (becareful!)
   4. observable change
      1. colour change
      2. gas produced
      3. apparent change in mass
         1. gas produced
      4. energy change
         1. released to surroundings
            1. exothermic
         2. absorbed from surroundings
            1. endothermic
         3. evaporation
            1. physical change
            2. also produces energy change
            3. BE CAREFUL!
   5. activation energy
      1. the "barrier" preventing a reaction from taking place
2. Collision Theory
   1. chemical reaction
      1. atoms, molecules, ions
      2. particles collide
         1. high enough energy
            1. break chemical bonds
            2. EFFECTIVE COLLISION
         2. too low energy
            1. bounce off
      3. bigger activation ennergy
         1. slower reaction
            1. slow
            2. rust
            3. quick
            4. petrol in cars
3. Rate of a Reaction
   1. rate "is proportional to" 1/time
      1. proportional to
   2. monitoring
      1. marble (calcium carbonate) + Hydrochloric acid ---> clacium chloride + carbon dioxide + water
      2. CaCO3 (s) + 2HCl (aq) ---> CaCl2(aq) + CO2(g) + H2O (l)
      3. measure volume of gas
      4. measure change in mass
   3. rate
      1. gradient of curve
      2. early in reaction
         1. steepest gradient
         2. quickest reaction
         3. max number of reacting particles
         4. max number of effective collisions
      3. mid section
         1. lower gradient
         2. lower rate
         3. fewer reacting particles
         4. fewer effective collisions
      4. top of curve
         1. horizontal
         2. gradient = zero
         3. reaction complete
         4. at least one reactant used up
         5. no further collisions