Collision Theory

This simulation illustrates collision theory for the reaction A + B giving C + D. Hard-sphere particles bounce in a box with speeds that follow the Maxwell-Boltzmann distribution for the chosen temperature. A collision reacts only if its energy along the line of centres reaches the activation energy. Students change the temperature, the activation energy and the concentration, and restart the run. Readouts show reactions so far, the reaction rate, the effective collisions and the Boltzmann factor. It explains why heat, concentration and a lower barrier all speed a reaction.

• Raise Temperature from 600 to 1200 K and compare the Reaction rate readout before and after.
• Lower Activation energy to 5 kJ/mol and see how many more collisions become effective.
• Increase Concentration from 30 to 60 of each and compare the number of Reactions so far.
• Watch the Effective collisions readout and note that most collisions only bounce.
• Press Restart and run the same settings twice to see the natural variation in the count.

1. 1State that a reaction needs a collision with at least the activation energy.
2. 2Explain how temperature affects the fraction of energetic collisions.
3. 3Describe how concentration changes the collision frequency.
4. 4Explain how lowering activation energy speeds up a reaction.

Questions teachers ask