Paper 2

• It gives an overview of everything that could come up on the paper
• It will allow you to do a last-minute cram on the night before the exam
• If you're taking GCSE Combined Science, watch out for the green headings at the top of the screen which tell you whenever there's triple science content that you'll need to skip
• You can also use the timestamps in the description below
• Rate of a chemical reaction


  Its speed, how fast it's going
• Measuring the rate of a chemical reaction

  1. How quickly the reaction is using up the reactants

  2. How quickly it is making products
• Calculations to work out the rate of a reaction


  An amount of one of the chemicals divided by the time that it takes to either make it or use it up
• The amount can be a mass in grams or a volume in centimetres cubed
• For higher tier, you should also be able to express rate in moles per second
• If a firm increases advertising

  Their demand curve shifts right, increasing the equilibrium price and quantity
• Marginal utility

  The additional utility (satisfaction) gained from the consumption of an additional product
• If you add up marginal utility for each unit you get total utility
• Collision theory

  Chemical reactions only happen when the reacting particles collide with each other with sufficient energy (activation energy)
• Ways to speed up the rate of a reaction

  • Increasing the pressure
  • Increasing the concentration
  • Increasing the surface area
  • Increasing the temperature
  • Adding a catalyst
• Increasing pressure

  Increases the rate by increasing the frequency of particle collisions
• Increasing concentration

  Increases the rate by increasing the frequency of particle collisions
• Increasing surface area

  Increases the rate by increasing the frequency of particle collisions
• Increasing temperature

  Increases the rate by increasing the frequency of particle collisions and by providing more particles with activation energy
• Catalyst


  A chemical that speeds up the rate of reaction without being used up or changed itself, by providing an alternative pathway with lower activation energy
• Required practical to investigate the effect of concentration on rate

  1. Collect gas over water or use a gas syringe to measure the amount of gas produced over time

  2. Measure the time for a reaction to become turbid (cloudy) due to a precipitate forming
• Reversible reaction


  A reaction where the products can react to form the original reactants, represented by a double-headed arrow
• If a reversible reaction is exothermic in one direction, it will be endothermic in the opposite direction
• Equilibrium


  The point where the forward and backward reactions are happening at the same rate, so the concentrations of reactants and products stop changing
• Le Chatelier's principle


  If a system at equilibrium is disturbed, it will shift to counteract the change and re-establish equilibrium
• Adding a reactant to a reversible reaction at equilibrium


  The system will shift to remove the added reactant
• Increasing pressure on a reversible reaction at equilibrium

  The system will shift towards the side with fewer gas molecules
• Heating a reversible reaction at equilibrium

  The system will shift towards the endothermic (backward) reaction
• Le Chatelier's principle tells me

  The system will shift to counteract that change and increase the pressure so it's going to move the equilibrium towards the higher pressure side which here is my reactants
• The backward reaction is favored because there are more molecules on the left
• The equilibrium will shift to the left


  Therefore the yield of sulfur trioxide will be lower
• If we heat up a reaction at equilibrium, the system will shift to try to cool it back down again
• The way it does this is by favoring the endothermic reaction
• The forward reaction is endothermic
• The forward reaction is favored


  Because that is what will cool my reaction back down
• The equilibrium shifts to the right
• The mixture will turn white
• Crude oil is a finite resource which means that it's going to run out
• Crude oil is found in rocks and made from the remains of ancient biomass which is mainly plankton that was buried in sediment
• Crude oil

  A mixture of hydrocarbons, compounds made of hydrogen and carbon only
• Alkanes


  A type of hydrocarbon found in crude oil