Collision theory explorer
Watch particles of A and B collide, see which collisions have enough energy to react, and link them to the Boltzmann distribution as you change temperature, concentration, particle size and catalyst.
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Learning objectives
- describe the effect of concentration, pressure, particle size and temperature on the rates of reactions and explain these effects in terms of collisions between reacting particles
- define the term catalyst and describe the effect of catalysts (including enzymes) on the rates of reactions
- explain how pathways with lower activation energies account for the increase in rates of reactions (see also 9(b))
- explain qualitatively, in terms of frequency of collisions, the effect of concentration changes on the rate of a reaction
- show understanding, including reference to the Boltzmann distribution, of what is meant by the term activation energy
- explain qualitatively, in terms of both the Boltzmann distribution and of collision frequency, the effect of temperature change on a rate constant (and hence, on the rate) of a reaction
- — explain that, in the presence of a catalyst, a reaction follows a different pathway, i.e. one of lower activation energy, giving a larger rate constant
- — interpret this catalytic effect in terms of the Boltzmann distribution
- Activation Energy and Boltzmann Distribution
- Catalysis and Enzymes
B as a gas, 1.00 mol/dm³ of A at 25 °C, without a catalyst (Eₐ = 10 kJ/mol). Press play to start the particles moving.
- A–B collisions
- — /s
- Successful collisions
- — /s
- Fraction successful
- — %
- AB formed
- 0
- Exposed B particles
- 0
Try this
0 of 4 doneRun for 30 s at two concentrations, with everything else the same. (not done yet)
More particles in the same space collide more often, so there are more successful collisions each second. The fraction that succeeds does not change.
Run for 30 s, then raise the temperature by at least 40 °C and run again. (not done yet)
Collisions become only a little more frequent, but a larger fraction of them have energy ≥ Eₐ: the shaded area grows. That is the main reason the rate rises.
Run for 30 s without the catalyst and 30 s with it, at the same temperature. (not done yet)
The catalyst gives a pathway with a lower Eₐ. The particles have the same energies, but more of their collisions now have enough energy to react.
Compare one lump of B with the powder, running each for 30 s. (not done yet)
Only particles on the surface can be hit. The powder exposes more of the same solid, so there are more collisions, and more successful ones, each second.