3.2.2 Kinetics - Effect of temperature on reaction rate
Students should:
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Changing the conditions - temperature
Increasing the temperature of a substance increases the average speed (Energy) of the particles and consequently the number of particles colliding with sufficient energy (Ea) to react. At higher temperatures there are more successful collisions and therefore a faster reaction.
Students often don't appreciate the significance of the two factors that change with increasing temperature:
- There are more collisions because the particles are moving faster on average
- The collisions have more energy
The second of these factors is by far the most important. This can be shown on the Maxwell Boltzmann plot. The area under the curve represents all the particles and the shaded are represents those particles which have sufficient energy to react if they collide. You can se that the shaded area increases by a high percentage for only small increases in temperature.
A simple (but wildly inaccurate) rule of thumb is that a reaction will double in rate for a 10ºC increase in temperature.
