Chemistry Paper 2

Ways to measure rate of reaction
1. Rate at which a reaction is used
2. Rate at which product is created
3. Temperature Change
Areas that effect the rate of reaction
1. Surface area of reactants
  1. More particles are exposed to the other reactants immedeiately
  2. Companies divide reactants into smaller pieces to increase rate of reaction
2. Concentration of reactants
  1. Greater chance of particles colliding
  2. Companies use highly concentrated chemicals to increase rate of reactions and for easier storage.
3. Temperature
  1. Increases particle's energy, so they move and collide more
  2. Companies are able to heat reactants more, increasing the rate of reaction.
4. Catalysts
  1. Lower activation energy needed
  2. Companies use catalysts, as they mean they don't need to heat it as much and they are reusable.
Conditions required for a reaction to happen
1. The reactants have to collide
2. The collision must have enough energy to react
Activation Energy
1. Activation energy is the energy needed for reactants to react
2. Chemical reactions can only occur when they have the right amount of activation energy
Catalysts
1. A substance that increases the rate of a chemical reaction without undergoing any physical change
2. It provides an alternative reaction pathway to the product
Companies need to decrease the rate of reaction as this means they don't have to pay workers as much (for shorter hours) and they can react more things in a shorter amount of time.
Practicals
1. Surface area
  1. Take 3 different sizes of marble chip: small, large and powder. Place each one in 20ml of hydrochloric acid and start a stopwatch. When it has dissolved, stop the stopwatch. The shortest time has the highest rate of reaction.
2. Concentration
  1. Take 5 different concentrations of acid.Put 10ml of Sodium thiosulphate in 20ml of each one and place the reaction over a dark mark. Start the stopwatch, and stop it when the mark can't be seen any more. The one with the lowest time has the highest rate of reaction.
3. Temperature
  1. Take hydrochloric acid at 4 different temperatures. In each one put a 5cm strip of magnesium after measuring the temperature. Wait 1 minute and measure the temperature again. The one with the highest temperature change has the highest rate of reaction.
4. Catalysts
  1. Take some sulphuric acid and zinc and put them into a flask connected to a gas syringe. Wait two minutes and measure the amount of gas in the gas syringe. Repeat this using a catalyst. The highest amount has the highest rate of reaction.
Hannah Farnell

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