Level 3
Applies knowledge and understanding of collision theory to explain both factors in detail although the reference to more collisions may only be made for one of the factors.
Quality of written communication does not impede communication of the science at this level (5-6 marks)
Quality of written communication does not impede communication of the science at this level (5-6 marks)
Level 2
Applies knowledge and understanding of collision theory to explain one of the factors in detail or partially explain both factors.
Quality of written communication partly impedes communication of the science at this level. (3-4 marks)
Quality of written communication partly impedes communication of the science at this level. (3-4 marks)
Level 1
Appreciation that the rate of any reaction depends on the number of collisions in whatever context it is used.
Quality of the written communication impedes communication of the science at this level. (1-2 marks)
Quality of the written communication impedes communication of the science at this level. (1-2 marks)
Level 0
Insufficient or irrelevant science. Answer not worthy of credit. (0 marks)
Additional Guidance
At all levels ignore reference to faster collisions and to more particles and ignore particles vibrate more.
allow answers that give the reverse argument but it must be very clear that this is what they have done.
Indicative scientific points at levels 2 and 3 may include:
rate increases with temperature because
allow - higher level answers for temperature that refer to more acid particles having sufficient energy to react or more acid particles having energy above that of the activation energy.
rate increases with powder because
Indicative scientific points at level 1 may include:
allow answers that give the reverse argument but it must be very clear that this is what they have done.
Indicative scientific points at levels 2 and 3 may include:
rate increases with temperature because
- acid particles move faster / acid particles have more energy
- more collisions between particles of acid and magnesium
allow - higher level answers for temperature that refer to more acid particles having sufficient energy to react or more acid particles having energy above that of the activation energy.
rate increases with powder because
- magnesium has greater surface area / powder has more magnesium particles exposed
- more collisions between particles of acid and magnesium.
Indicative scientific points at level 1 may include:
- more collisions gives a faster reaction even if referring to concentration or pressure
- link between number of collisions and rate of reaction
Level 3 Answer for 6 marks...
The rate of reaction increases when the temperature increases because the acid particles have more energy. This means they move faster and will collide more frequently with the magnesium.
The rate of reaction increases when powder is used instead of magnesium ribbon because the magnesium powder has a greater surface area. This means the acid particles will collide more frequently with the magnesium.
As you can see, it doesn't require pages of writing. In that answer we have explained both factors and made reference to there being more frequent collisions.
Point to note...If you had missed out the word collisions in your answer then that 6 mark answer drops to a zero. If they say collision theory, always use the word collisions.
The rate of reaction increases when powder is used instead of magnesium ribbon because the magnesium powder has a greater surface area. This means the acid particles will collide more frequently with the magnesium.
As you can see, it doesn't require pages of writing. In that answer we have explained both factors and made reference to there being more frequent collisions.
Point to note...If you had missed out the word collisions in your answer then that 6 mark answer drops to a zero. If they say collision theory, always use the word collisions.