Chemistry · The rate and extent of chemical change. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Collision theory says that particles react only when they collide, and only if they collide with enough energy. The minimum energy needed is the activation energy. Anything that makes collisions more frequent, or gives more collisions enough energy, makes the reaction faster.
A higher concentration, a higher gas pressure or a larger surface area makes collisions more frequent. A higher temperature does two things: the particles move faster, so they collide more often, and more of the collisions have the activation energy.
A catalyst speeds up a reaction without being used up. It gives the reaction a different pathway with a lower activation energy.
Students write that there are 'more collisions' and lose the mark. Say the collisions are more frequent (more collisions each second). Also, only temperature and catalysts change the share of collisions that succeed.
Answer: The total surface area becomes three times larger (54 cm2 to 162 cm2).
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