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RATES OF REACTION A guide for GCSE students

RATES OF REACTION A guide for GCSE students. 2010 SPECIFICATIONS. KNOCKHARDY PUBLISHING. RATES OF REACTION. INTRODUCTION

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RATES OF REACTION A guide for GCSE students

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  1. RATES OF REACTION A guide for GCSE students 2010 SPECIFICATIONS KNOCKHARDY PUBLISHING

  2. RATES OF REACTION INTRODUCTION This Powerpoint show is one of several produced to help students understand selected GCSE Chemistry topics. It is based on the requirements of the AQA specification but is suitable for other examination boards. Individual students may use the material at home for revision purposes and it can also prove useful for classroom teaching with an interactive white board. Accompanying notes on this, and the full range of AS and A2 Chemistry topics, are available from the KNOCKHARDY WEBSITE at... www.knockhardy.org.uk All diagrams and animations in this Powerpoint are original and created by Jonathan Hopton. Permission must be obtained for their use in any commercial work.

  3. THE IMPORTANCE OF REACTION RATE Being able to speed up or slow down chemical reactions is important in industry and in everyday life. Reactions… which take place slowly may need to be speeded up which are too fast may need to be controlled may need to be carried out at a lower temperature to save energy or be safer

  4. THE IMPORTANCE OF REACTION RATE Being able to speed up or slow down chemical reactions is important in industry and in everyday life. Reactions… which take place slowly may need to be speeded up which are too fast may need to be controlled may need to be carried out at a lower temperature to save energy or be safer Changes in temperatureconcentration of solution gas pressuresurface area of solids plus the presence of catalysts all affect the rate of reactions.

  5. COLLISION THEORY Explains why the rate of reaction changes It states ‘particles must COLLIDE before a reaction can take place’ NO COLLISION No chance of a reaction taking place COLLISION A reaction might now take place

  6. COLLISION THEORY Explains why the rate of reaction changes It states ‘particles must COLLIDE before a reaction can take place’ ‘not all collisions lead to a reaction’ BUT NO COLLISION No chance of a reaction taking place COLLISION A reaction might now take place

  7. COLLISION THEORY Explains why the rate of reaction changes It states ‘particles must COLLIDE before a reaction can take place’ ‘not all collisions lead to a reaction’ ‘reactants must have at least a minimum amount of energy known as the ACTIVATION ENERGY in order to react’ BECAUSE

  8. NOT ENOUGH ENERGY No chance of a reaction taking place ENOUGH ENERGY A reaction will now take place COLLISION THEORY Explains why the rate of reaction changes It states ‘particles must COLLIDE before a reaction can take place’ ‘not all collisions lead to a reaction’ ‘reactants must have at least a minimum amount of energy known as the ACTIVATION ENERGY in order to react’

  9. COLLISION THEORY Explains why the rate of reaction changes According to collision theory, to increase the rate of reaction you therefore need...

  10. COLLISION THEORY Explains why the rate of reaction changes According to collision theory, to increase the rate of reaction you therefore need... more frequent collisions

  11. COLLISION THEORY Explains why the rate of reaction changes According to collision theory, to increase the rate of reaction you therefore need... more frequent collisions increase particle speed or have more particles present

  12. COLLISION THEORY Explains why the rate of reaction changes According to collision theory, to increase the rate of reaction you therefore need... more frequent collisions increase particle speed or have more particles present more successful collisions

  13. COLLISION THEORY Explains why the rate of reaction changes According to collision theory, to increase the rate of reaction you therefore need... more frequent collisions increase particle speed or have more particles present more successful collisions give particles more energy or lower the activation energy

  14. INCREASING THE RATE OF REACTION The following methods can be used • INCREASE THE SURFACE AREA OF SOLIDS • INCREASE TEMPERATURE • ADD A CATALYST • INCREASE THE CONCENTRATION OF REACTANTS • INCREASE THE PRESSURE OF ANY GASES • SHINE LIGHT (a limited number of reactions)

  15. INCREASING SURFACE AREA

  16. INCREASING SURFACE AREA • Increasing surface area increases chances of a collision • - more particles are exposed

  17. INCREASING SURFACE AREA • Increasing surface area increases chances of a collision • - more particles are exposed • Powdered solids react quicker than larger lumps

  18. INCREASING SURFACE AREA • Increasing surface area increases chances of a collision • - more particles are exposed • Powdered solids react quicker than larger lumps • Catalysts (e.g. in catalytic converters) are in a finely • divided form for this reason

  19. INCREASING SURFACE AREA • Increasing surface area increases chances of a collision • - more particles are exposed • Powdered solids react quicker than larger lumps • Catalysts (e.g. in catalytic converters) are in a finely • divided form for this reason 1 3 3 SURFACE AREA 9+9+3+3+3+3 = 30 sq units

  20. INCREASING SURFACE AREA • Increasing surface area increases chances of a collision • - more particles are exposed • Powdered solids react quicker than larger lumps • Catalysts (e.g. in catalytic converters) are in a finely • divided form for this reason 1 3 3 SURFACE AREA 9+9+3+3+3+3 = 30 sq units

  21. INCREASING SURFACE AREA • Increasing surface area increases chances of a collision • - more particles are exposed • Powdered solids react quicker than larger lumps • Catalysts (e.g. in catalytic converters) are in a finely • divided form for this reason CUT THE SHAPE INTO SMALLER PIECES 1 3 3 SURFACE AREA 9+9+3+3+3+3 = 30 sq units

  22. INCREASING SURFACE AREA • Increasing surface area increases chances of a collision • - more particles are exposed • Powdered solids react quicker than larger lumps • Catalysts (e.g. in catalytic converters) are in a finely • divided form for this reason 1 CUT THE SHAPE INTO SMALLER PIECES 1 1 1 3 3 SURFACE AREA 9+9+3+3+3+3 = 30 sq units NEW SURFACE AREA 9 x (1+1+1+1+1+1) = 54 sq units

  23. INCREASING SURFACE AREA • Increasing surface area increases chances of a collision • - more particles are exposed • Powdered solids react quicker than larger lumps • Catalysts (e.g. in catalytic converters) are in a finely • divided form for this reason 1 CUT THE SHAPE INTO SMALLER PIECES 1 1 1 3 3 SURFACE AREA 9+9+3+3+3+3 = 30 sq units NEW SURFACE AREA 9 x (1+1+1+1+1+1) = 54 sq units

  24. INCREASING THE TEMPERATURE

  25. INCREASING THE TEMPERATURE • increasing the temperature increases the rate of a reaction • particles get more energy - more overcome the energy barrier • particle speeds also increase - collisions are more frequent

  26. INCREASING THE TEMPERATURE • increasing the temperature increases the rate of a reaction • particles get more energy - more overcome the energy barrier • particle speeds also increase - collisions are more frequent ENERGY CHANGES DURING A REACTION During a reaction the enthalpy (a form of energy) rises to a maximum, then falls START OF REATION END OF REATION

  27. INCREASING THE TEMPERATURE • increasing the temperature increases the rate of a reaction • particles get more energy - more overcome the energy barrier • particle speeds also increase - collisions are more frequent ENERGY CHANGES DURING A REACTION During a reaction the enthalpy (a form of energy) rises to a maximum, then falls A minimum of energy is needed to overcome the ACTIVATION ENERGY (Ea) ACTIVATION ENERGY

  28. INCREASING THE TEMPERATURE • increasing the temperature increases the rate of a reaction • particles get more energy - more overcome the energy barrier • particle speeds also increase - collisions are more frequent ENERGY CHANGES DURING A REACTION During a reaction the enthalpy (a form of energy) rises to a maximum, then falls A minimum of energy is needed to overcome the ACTIVATION ENERGY (Ea) Only reactants with energy equal to, or greater than, this value will react. ACTIVATION ENERGY

  29. INCREASING THE TEMPERATURE • increasing the temperature increases the rate of a reaction • particles get more energy - more overcome the energy barrier • particle speeds also increase - collisions are more frequent ENERGY CHANGES DURING A REACTION During a reaction the enthalpy (a form of energy) rises to a maximum, then falls A minimum of energy is needed to overcome the ACTIVATION ENERGY (Ea) Only reactants with energy equal to, or greater than, this value will react. If they don’t have enough energy they will not get over the barrier. ACTIVATION ENERGY

  30. INCREASING THE TEMPERATURE • increasing the temperature increases the rate of a reaction • particles get more energy - more overcome the energy barrier • particle speeds also increase - collisions are more frequent ENERGY CHANGES DURING A REACTION During a reaction the enthalpy (a form of energy) rises to a maximum, then falls A minimum of energy is needed to overcome the ACTIVATION ENERGY (Ea) Only reactants with energy equal to, or greater than, this value will react. If they have enough energy they will get over the barrier. ACTIVATION ENERGY

  31. INCREASING THE TEMPERATURE • increasing the temperature increases the rate of a reaction • particles get more energy - more overcome the energy barrier • particle speeds also increase - collisions are more frequent ENERGY CHANGES DURING A REACTION During a reaction the enthalpy (a form of energy) rises to a maximum, then falls A minimum of energy is needed to overcome the ACTIVATION ENERGY (Ea) Only reactants with energy equal to, or greater than, this value will react. If more energy is given to the reactants then they are more likely to react. ACTIVATION ENERGY

  32. INCREASING THE TEMPERATURE • increasing the temperature increases the rate of a reaction • particles get more energy - more overcome the energy barrier • particle speeds also increase - collisions are more frequent ENERGY CHANGES DURING A REACTION During a reaction the enthalpy (a form of energy) rises to a maximum, then falls A minimum of energy is needed to overcome the ACTIVATION ENERGY (Ea) Only reactants with energy equal to, or greater than, this value will react. If more energy is given to the reactants then they are more likely to react. ACTIVATION ENERGY

  33. ADDING A CATALYST

  34. ADDING A CATALYST • Catalysts provide an alternative reaction pathway with a lower • Activation Energy (Ea)

  35. ADDING A CATALYST • Catalysts provide an alternative reaction pathway with a lower • Activation Energy (Ea) • Decreasing the Activation Energy means that more particles will • have sufficient energy to overcome the energy barrier and react

  36. ADDING A CATALYST • Catalysts provide an alternative reaction pathway with a lower • Activation Energy (Ea) • Decreasing the Activation Energy means that more particles will • have sufficient energy to overcome the energy barrier and react WITHOUT A CATALYST

  37. ADDING A CATALYST • Catalysts provide an alternative reaction pathway with a lower • Activation Energy (Ea) • Decreasing the Activation Energy means that more particles will • have sufficient energy to overcome the energy barrier and react NEW PATHWAY WITHOUT A CATALYST WITH A CATALYST

  38. ADDING A CATALYST • Catalysts provide an alternative reaction pathway with a lower • Activation Energy (Ea) • Decreasing the Activation Energy means that more particles will • have sufficient energy to overcome the energy barrier and react • Catalysts remain chemically unchanged at the end of the reaction • - they are not used up

  39. ADDING A CATALYST • Catalysts provide an alternative reaction pathway with a lower • Activation Energy (Ea) • Decreasing the Activation Energy means that more particles will • have sufficient energy to overcome the energy barrier and react • Catalysts remain chemically unchanged at the end of the reaction • - they are not used up • Using catalysts avoids the need for extra heat- safer and cheaper

  40. ADDING A CATALYST • Catalysts provide an alternative reaction pathway with a lower • Activation Energy (Ea) • Decreasing the Activation Energy means that more particles will • have sufficient energy to overcome the energy barrier and react • Catalysts remain chemically unchanged at the end of the reaction • - they are not used up • Using catalysts avoids the need for extra heat - safer and cheaper • They are used in industry especially where an increase in • temperature results in a lower yield due to a shift in equilibrium

  41. ADDING A CATALYST • Catalysts provide an alternative reaction pathway with a lower • Activation Energy (Ea) • Decreasing the Activation Energy means that more particles will • have sufficient energy to overcome the energy barrier and react • Catalysts remain chemically unchanged at the end of the reaction • - they are not used up • Using catalysts avoids the need for extra heat - safer and cheaper • They are used in industry especially where an increase in • temperature results in a lower yield due to a shift in equilibrium • Examples include the Haber and Contact Processes

  42. CATALYSTS – USEFUL POINTS Catalysts are widely used in industry because they… 1 Allow reactions to take place SAVE ENERGY (lower Ea) at lower temperatures REDUCE CO2 OUTPUT 2 Enable different reactions to be used BETTER ATOM ECONOMY REDUCE WASTE 3 Are often enzymes GENERATE SPECIFIC PRODUCTS OPERATE EFFECTIVELY AT ROOM TEMPS 4 Have great economic importance POLY(ETHENE) in the industrial production of SULPHURIC ACID AMMONIA ETHANOL 5 Can reduce pollution CATALYTIC CONVERTERS

  43. INCREASING THE CONCENTRATION OF SOLUTIONS

  44. INCREASING THE CONCENTRATION OF SOLUTIONS Increasing concentration = more frequent collisions = increased rate of reaction Low concentration fewer collisions Higher concentration more collisions = FASTER

  45. INCREASING THE PRESSURE OF GASES

  46. INCREASING THE PRESSURE OF GASES • increasing the pressure forces gas particles closer together

  47. INCREASING THE PRESSURE OF GASES • increasing the pressure forces gas particles closer together • this increases the frequency of collisions so the rate increases

  48. INCREASING THE PRESSURE OF GASES • increasing the pressure forces gas particles closer together • this increases the frequency of collisions so the rate increases • many industrial processes occur at high pressure to increase • the rate... but it can adversely affect the yield

  49. INCREASING THE PRESSURE OF GASES • increasing the pressure forces gas particles closer together • this increases the frequency of collisions so the rate increases • many industrial processes occur at high pressure to increase • the rate... but it can adversely affect the yield

  50. INCREASING THE PRESSURE OF GASES • increasing the pressure forces gas particles closer together • this increases the frequency of collisions so the rate increases • many industrial processes occur at high pressure to increase • the rate... but it can adversely affect the yield • more particles in a given volume = greater pressure

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