4.20 explain the effects of changes in surface area of a solid, concentration of solutions, pressure of gases and temperature on the rate of a reaction in terms of particle collision theory

Collision theory says that to react particles must:
Collide with enough energy to react
Collide in the right orientation to react (the more frequent the collisions, the more likely this is)

Surface area

• Particles collide more frequently if there is more surface area, as there is more contact between the reactants. Faster rate of reaction.

Concentration/ pressure

• There is more chance of particles colliding at a higher concentration/pressure, so they react more often. Faster rate of reaction.

Temperature

• Particles move about more and will collide more frequently the higher the temperature; react more often. Increases the rate of reaction.

Catalyst

• Provides an alternative pathway for the reaction to start which requires a lower activation energy.