4.3.1 Collision Theory

Question 1

A chemical reaction can only occur if…

Answer 1

…the reactant particles collide with enough energy.

Question 2

What is the amount of energy the particles need to react called?

Answer 2

Activation energy

Question 3

What two factors does the overall rate of reaction depend on?

Answer 3

• Collision frequency: how often do the particles collide with each other?
• Percentage success: what percentage of the collisions have enough energy?

Question 4

What are four common factors affecting the rate of reaction?

Answer 4

• Solid surface area (collision frequency)
• Solution concentration (collision frequency)
• Temperature (percentage success)
• Catalysts (percentage success)

Question 5

Why does a high solid surface area increase rate of reaction?

Answer 5

More surfaces of the solid are exposed and accessible to collisions. There are more frequent collisions and more frequent successful collisions.

Question 6

Why does a high solution concentration increase rate of reaction?

Answer 6

There are more particles per unit volume. Therefore there are more frequent collisions and more successful collisions per unit time.

Question 7

Why does a high temperature increase rate of reaction?

Answer 7

The particles have more kinetic energy, meaning the percentage of collisions with energy above activation energy is higher. This means there are more frequent successful collisions.

Question 8

Why does a catalyst increase rate of reaction?

Answer 8

Catalysts provide an alternative route with a lower activation energy, so the percentage of collisions with enough energy is higher and there are more frequent successful collisions.