Speed of reactions

• what is a variable?


  different conditions which can affect the rate of a chemical reaction
• what are the 3 main variables which can affect the rate of a chemical reaction?


  particle size of a solid, concentration of a liquid, temperature of a solution
• how can you carry out a fair test?


  keep the mass of solids and the volume of solutions constant
• what happens with a large surface area?


  the faster the speed of reaction
• what happens as the particle size decreases?


  the faster the speed of reaction
• what happens when the size of the particles get smaller?


  the faster the speed of reaction
• what happens when the temperature of solution increases?


  the faster the speed of reaction
• what happens when the concentration of solution increases?


  the faster the speed of reaction
• how can the average rate of a reaction be measured?


  using information about changes that have occurred during the reaction
• what is the formula used for calculating the average rate of a reaction?


  rate = change in quantity divided by change in time taken
• what is the units used in volume?


  cm3s-1
• what is the units used in mass?


  _gs-1
• what is the units used in concentration?


  mol l-1 s-1
• when do rates get slower?


  when the reactants are used up
• what is the collision theory?


  the theory that chemical reactions only occur when particles collide with sufficient energy
• what is a catalyst?


  substance which speeds up a chemical reaction and does not get used up
• give the name of one industrial catalyst and give its use


  nickel is used to speed up the reaction to form margarine
• what is the catalyst material used in cars?


  platinum
• what is an enzyme?


  a biological catalyst that speeds up reactions in plants and animals
• what does amylase do in saliva?


  speeds up the breakdown of starch and sugars