Catalysts

A catalyst is a substance that speeds up a reaction without being chemically used up.

How they work

• Provide a different reaction pathway,

• One that requires a lower activation energy.

Lower activation energy means more likely for collisions to be successful, therefore faster reaction rate

Cyclist Analogy for Activation Energy and Catalysts

Imagine a cyclist travelling from one side of a hill to the other:

Without a Catalyst — The Steep Hill

• The cyclist must pedal up and over a tall, steep hill.

• This hill represents the activation energy — the minimum amount of energy needed for the reaction to start.

• If the cyclist doesn’t push hard enough, they won’t reach the top and will roll back down.

• In the same way, particles that collide without enough energy don’t react and simply bounce apart.

With a Catalyst — The Tunnel

• Now imagine there’s a tunnel dug straight through the hill.

• The tunnel offers a lower, easier route that requires much less effort from the cyclist.

• This tunnel represents the alternative reaction pathway created by a catalyst.

• The journey becomes quicker and requires less energy, even though the cyclist still ends up on the same side.

Why the Analogy Works

• Hill = activation energy barrier

• Tunnel = catalyst pathway

• Cyclist = reacting particles

• Getting to the other side = products forming

• The height of the hill doesn’t change — but the route taken does.