Chemistry C2.4

  • Created by: juddr12
  • Created on: 24-04-14 09:55

C2 4.1

The rate of a reaction is how fast one is. You can work out the rate by measuring how much reactant is used or how much is formed and dividing it by time.

To work out an average rate, you have to work out the time for a certain amount of either a solid or a gas to form.

One can easily measure rate when looking at a reactant-time or product-time graph. The gradient of the line will tell you the rate. The steeper the slope, the faster the rate of reaction.

However, graphs may also show change in pH or concentration or colour of a reaction.

C2 4.2

Collision theory states that reactions only occur when particles collide and with enough energy. Factors increase rates of reactions for a number of reasons. However, they all result in "more frequent collisions" (I will say MFC for short, but do not do this in the exam!).

  • Temperature - increases the amount of energy took into reaction;makes particles move around faster so MFC.
  • Concentration of solutions or pressure of games - move particles to collide or smaller space so MFC.
  • Catalyst - lowers the activation energy needed for a reaction to take place, therefore particles with little energy can still react. This leads to MFC.
  • Increase of surface area by grinding solids - more particles are accessible for reactions, so MFC.

C2 4.3

Even a small change in temperature has a large effect on the rate of reactions, because it not only makes particles move faster and collide more frequently but increases the amount of energy in a reaction

We like decreasing food temperature to


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