Paper 1

• Rate of reaction

  How quickly a reaction happens
• Mean rate

  The rate of reaction over a period of time
• Experiment: Reacting hydrochloric acid and sodium thiosulfate

  Product formed turns the solution cloudy, increased turbidity, stop the timer when the cross is no longer visible
• Experiment: Measuring volume of gas produced

  Use a gas syringe connected to the reaction vessel, graph shows quantity on y-axis and time on x-axis, curve starts steeply and levels out when reaction is completed
• Calculating rate at any time

  Draw a tangent at that point on the graph, take the change in quantity and divide by time
• Factors that increase the rate of reaction

  • Increasing concentration of reactants in solution
  • Increasing pressure of gas reactants
  • Increasing surface area of solid reactants by crushing into a powder
  • Increasing temperature
  • Adding a catalyst
• Reversible reactions


  Reactions where products can return to original reactants
• Closed system


  No particles or energy going in or out, both forward and reverse reactions continually take place until rates are equal
• Le Chatelier's principle

  If a system at equilibrium is subjected to a change, the system will adjust to counteract that change
• Increasing pressure in a reaction with more moles on the left

  Favors the forward reaction until equilibrium is reached, shifting the position of equilibrium to the right
• Reducing pressure in a reaction with more moles on the left

  Shifts the position of equilibrium to the left
• Changing concentration in a solution

  Affects the position of equilibrium in a similar way to changing pressure in a gas reaction
• Proportion of ammonia increases

  Position of equilibrium shifts to the right
• Reducing pressure

  Shifts the position of equilibrium to the left
• Concentration in solutions

  Follows the same principle as in reactions
• Removing molecules from one side of the reaction

  Shifts the position of equilibrium in that direction to produce more
• Increasing temperature


  Makes it harder for a reaction to produce heat, favoring the endothermic reaction
• Higher temperature favors endothermic reaction


  Supplies the energy required for an endothermic reaction
• Colder temperature favors exothermic reaction

  Higher temperature favors endothermic reaction
• Breaking down of reactant in a reaction

  Endothermic reaction
• Forward reaction is exothermic


  Reverse reaction must be endothermic and vice versa
• Organic compounds have carbon forming the backbone of the molecules
• Crude oil is the result of Plankton being buried under water a long time ago and consists mostly of hydrocarbons
• Most hydrocarbons in crude oil are alkanes, chains of single covalently bonded carbon atoms surrounded by hydrogen atoms
• General formula for alkanes is CNH2N+2
• All alkane names end with 'ane' and the beginning of the name indicates the chain length
• Fractional distillation is used to separate different length alkanes in crude oil
• Longer alkanes have higher boiling points due to stronger intermolecular forces
• LPG contains a range of chain length alkanes up to four carbons long
• Petrol is used in cars, kerosene for jet fuel, diesel oil for cars and lorries, and heavy fuel oil for large ships
• Complete combustion of alkanes with oxygen produces carbon dioxide and water
• Longer fractions of alkanes are more viscous, while shorter fractions are more flammable
• Alkanes can be used to make solvents, lubricants, detergents, and polymers for plastics
• Polymers can be made from alkenes, which have a carbon-carbon double bond
• Alkenes are unsaturated hydrocarbons, while alkanes are saturated
• Bromine water turns colorless when added to an alkene, indicating saturation
• Alkenes can be saturated by chlorine, iodine, and water
• Alkenes can be tested with bromine water to check for unsaturation
• Alkenes can form products like one, two-dibromoethane when saturated
• Alkanes are saturated and cannot undergo further saturation