4.3 Collision theory

surface area concentration temperature catalyst

more solid is exposed to other particles more frequent collisions per unit time more successful collisions per unit time

more particles per unit volume more frequent collisions per unit time more successful collisions per unit time

particles have more kinetic energy more frequent collisions with enough energy per unit time more successful collisions per unit time

provide an alternative route with a lower activation energy more collisions have enough energy to react more frequent collisions per unit time more successful collisions per unit time

dissolve more solute particles

make the reaction vessel smaller

disappearing cross experiment method: react sodium thiosulphate solution with hydrochloric acid - keep mixing until you can no longer see the cross - record the time taken for the cross to disappear result: rate and concentration are proportional control variables: total volume of solution, concentration of HCl, temperature

marble chip experiment method: react calcium carbonate (marble) chips with hydrochloric acid results: graph plotted with the higher surface area and the original surface area higher SA has a steeper start - rate increases so volume CO2 is increasing faster same final volume- total amounts of reactants hasn’t changed - eventually produces same amount of CO2 control variables: mass marble chips, volume of HCl, temperature

cutting or grinding up the solid

react magnesium with HCl magnesium disappears measure time taken for magnesium to disappear and record the temperature of the HCl control: mass and SA of Mg, volume of HCl results: not a straight line

heating

1/time taken

hydrogen peroxide experiment catalysed by manganese oxide input: which catalyst is being used output: volume of O2 control: volume and concentration of H2O2, temperature, mass/SA of catalyst results: more effective catalysts increase rate more efficiently (steeper line)

The amount of energy particles need to react