Collision Theory

Question 1

Define rate of reaction

Answer 1

Speed at which the reaction occurs

Question 2

What makes an effective collision?

Answer 2

1. Needs enough energy
2. Have correct orientation

Question 3

Define activation energy

Answer 3

Minimum amount of energy needed for particles to collide for the reaction to take place

Question 4

What are the rates of reactions and what influences them?

Answer 4

Slow - not a lot of successful collisions
Fast - increased successful collisions

INFLUENCES:
1. Heat - energy - temperature
2. Concentration (number of atoms)
3. Surface area
4. Pressure - gas
5. Catalysts

Question 5

Why does temperature affect the rate of reaction?

Answer 5

Higher temperature = faster rate of reaction
1. At higher temperatures, particles have more energy - move faster and are more likely to collide with other particles - increased collision rate
2. When the particles collide, they do so with more energy, and so the number of successful reactions increase

Question 6

Why does concentration affect the rate of reaction?

Answer 6

The higher the concentration of a dissolved reactant, the faster the rate of reaction
At a higher concentration = more particles in the same amount of space = more likely to collide = more likely to react

Question 7

Why does pressure affect the rate of reaction?

Answer 7

If the pressure increases, the space in which gas particles are moving becomes smaller
This makes the gas particles come closer together, which increases the frequency of collisions = more likely to react

Question 8

Why does surface area affect the rate of reaction?

Answer 8

Any reaction involving a solid can only take place at the surface of the solid
If the solid splits into pieces = more surface area
This means that there is an increased surface are for the reactant particles to collide with
Smaller pieces = larger surface area = more collisions = greater chance of reaction

Question 9

Define catalyst

Answer 9

Substances that increase the rate of reaction without being used up in the reaction

Question 10

Why do catalysts affect the rate of reaction?

Answer 10

Catalysts never produce more than one product - produce the same amount more quickly
Catalysts work by lowering the activation energy (EA)