Question 3
Why does raising the temperature increase the rate of reaction?
The right answer is the one marked above.
Because the particles gain kinetic energy and the number of collisions in unit time goes up. At a higher temperature the particles move faster.
Heating changes neither the mass, the size nor the number of the particles. All it changes is how fast they move — and that is enough, because it raises both the number and the energy of the collisions.