rate of reactions

• core practical (reaction for how surface area affects the rate of reaction)

  measuring the production of gas

  • measure 40cm^3 of dilute hydrochloric acid into a conical flask
  • add 5g of small marble chips to a flask (add stopper and start stopwatch)
  • note the total volume of gas produced after every 30 seconds until reaction has finished
  • repeat using 5g of large marble chips
• core practical (reaction for how temperature affects the rate of reaction)

  observing a colour change

  • place 50cm^3 of sodium thiosulfate solution into 300cm^3 conical flask
  • measure 5cm^3 of dilute hydrochloric acid in a test tube
  • place the conical flask in a water bath at a certain temp
  • place the test tube in a rack in same water bath , and record the temp
• core practical (reaction for how temperature affects the rate of reaction)

  observing a colour change

  • after 5 mins, remove flask and place on piece of white paper marked with a cross, add acid to thiosulphate and start the stopwatch and stop it when you are unable to see the cross anymore
  • note the time and take the final temp
  • repeat with three or four different temperatures between 20 and 50 degrees
• $rate\ of\ reaction\ =$$\ \frac{amount\ of\ product\ formed}{time}$ OR $rate\ of\ reaction\ =$$\ \frac{amount\ of\ react@nt\ used}{time}$
• rate of reaction is the speed at which a reaction occurs
• for a chemical reaction to occur the reactant particles must collide with enough energy to react the minimum amount of energy needed for a reaction to occur is called activation energy, during successful collisions this energy helps break bonds for atoms to be rearranged to make new substances
• the rate of reaction is affected by :

  • concentration
  • temperature
  • surface area to volume ratio
  • pressure of gas
• concentration


  increasing concentration of solutions increases the rate of reaction as there are more reacting particles in the same volume therefore collisions occur more often
• surface area to volume ratio

  increasing surface are to volume ratio causes the rate of reaction to increase as there is more surface area for collisions to occur
• temperature


  increasing temperature increases the rate or reaction as the particles gain kinetic energy so they collide more frequently
• pressure


  increasing pressure in reacting gases increases the rate of reaction as it increases the number of particles in a given volume therefore increases the frequency of collisions
• a catalyst is a substance that speeds up a reaction without being used up, it lowers the activation energy meaning less energy is required for the reaction to begin
• enzymes are biological catalysts and enzymes are used in the production of alcoholic drinks