C2

• collision theory

  atoms, ions, molecules must collide in order to reacts
• pressure

  measure of force exerted by unit area
• what does the catalyst do in the reaction?

  LOWERS the activation energy/creates an alternative pathway
• slow reaction

  rusting of iron/chemical weathering

  fast reactions

  burning/explosions
• rate of reaction graphs

  steeper line = faster rate

  flat = reaction done

  higher line = more reactant and product
• factors effecting rate of reaction

  temp - more energy = collide more freq

  concentration/pressure - more particles in an area = more freq colllisions

  surface area - smaller pieces = more area for collisions
• precipitate

  = solid formed in a reaction
• precipitate and colour change showing rate of reaction

  observe how long it takes for a solution to lose/gain colour

  observe how long it takes solution to become cloudy
• change in MASS

  • put reaction in scale
  • if gas is produced = mass will decrease
  • quicker - faster the reaction
• volume of GAS

  • gas syringe to measure vol of gas being produced
  • more gas given off = faster rate
• reaction rate from graphs

  mean rate? - overall change in y-axis/time taken

  rate at a point? - draw a tangent and find gradient
• reversible reaction

  a+b = c+d
• rate of reversible reaction

  reactants react - concentration falls = forward reaction slows

  products are made - concentration rises = backward reaction speeds up

  eventually forward reac is the same rate as backward reac = equilibrium
• equilibrium

  both reactions happening - but no overall effect

  unchanging balance of products and reactants only occur in a closed system
• conditions affecting position of equilibrium

  temp

  pressure

  concentration of reactants/products
• exo/endo reversible reaction

  if endo is in one direction = exo in the other
• La Chatelier's principle

  if you change the conditions of a reversible reaction at equilibrium - system will try to counteract that change