Controlling Reactions

• what is collision theory

  the theory that chemical reactions can only occur when reacting particles collide with each other with sufficient energy
• what is the minimum activation energy

  the minimum amount of energy particles must have in order to collide successfully
• how can particle size affect the rate of reaction

  when particle size increases, the surface area increases. So more particles are exposed for collisions. Therefore the frequency of successful collisions increases.
• what is concentration

  the amount of substance dissolved in a given volume
• what are the 2 products when an acid and metal reacts

  a salt and a hydrogen gas
• how does concentration affect the rate of reaction


  when the concentration increases, the rate of reaction increases. As there are more particles in the same volume, the particles are more crowded . Therefore the frequency of successful collisions increases.
• how does temperature affect the rate of reaction

  when temperature increases the rate of reaction increases as the particles have been given more energy so they will move faster. Therefore, the frequency of successful collisions increases.
• how does pressure affect the rate of reaction

  when pressure increases, the rate of reaction increases as there are the same number of particles in a smaller volume meaning the particles are more crowded. Therefore, the frequency of successful collisions increases.
• list 4 ways you can measure the rate of reaction

  1 change in mass

  2 change in colour

  3 percipitate reactions

  4 volume produced
• list the 5 ways the rate of reaction can be affected

  1 temperature

  2 catalysts

  3 surface area / particle size

  4 pressure

  5 concentration
• how can you work out the average rate of reaction on a graph

  y/x
• how can you work at the rate of reaction at a certain point on a graph

  1 make a tangent line on the point

  2 gradient = y/x
• how does a catalyst affect the rate of reaction


  a catalyst speeds up the rate of reaction by providing an alternate reaction pathway with a lower minimum activation energy. More particles have the minimum activation energy therefore the frequency of successful collisions increases. The catalyst remains unchanged at the end of the reaction.
• catalysts cannot get used up in a reaction therefore they can be used over again.
• what is meant by the 'rate of reaction'


  a measure of how quickly reactants are used or products are formed
• Describe the experiment to measure the volume of gas produced (using a water basin)


  1 add hydrochloric acid to a conical flask

  2 fill a measuring cylinder with water and turn it upside down into a semi-filled water basin (ensuring it is still full) with a tube connected to the conical flask

  3 then add magnesium ribbon into the acid, add the bun to the flask and start the stopwatch

  4 record the volume of gas releases every 10 seconds until no more gas is lost
• Describe an experiment to measure the volume of gas produced (using a gas syringe)


  1 add hydrochloric acid to a conical flask

  2 connect a gas syringe to the conical flask using a tube

  3 then add magnesium ribbon into the acid, add the bun to the flask and start the stopwatch

  4 record the volume of gas releases every 10 seconds until no more gas is lost
• Describe an experiment to measure how temperature effects rate of reaction 


  1 get a piece of paper with a large cross drawn in and place it under a beaker

  2 in the beaker mix the reactants and observe how long it takes for the cross to not be visible

  3 repeat with the same substances but at different temperatures to see a difference
• Describe an experiment that measures how particle size effects the rate of reaction 


  1 add dilute hydrochloric acid to a conical flask and stopper it with cotton wool

  2 place the flask on a scale

  3 record the initial weight and add magnesium powder to the flask and record the mass at regular intervals until the reaction has stopped

  4 repeat the experiment with different sizes of magnesium