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Particle size 对 rate of reaction 的影响是非常直观的。是一勺盐在水里溶化的快，还是一块盐在水里溶化的快？当然是粉末状的（powder）的盐。但是一定要记住decrease particle size = increase surface area。

满分回答：Decreasing the particle size of the solid will increase the fraction of particles available for collision, increasing frequency of effective collision & hence the rate of reaction.

Concentration 和 pressure 其实差不多，唯一的区别是 liquid 是 concentration, 而 gaseous reactants 是 pressure。

满分回答：Increasing the concentration of a reactant (or the pressure of a gaseous reactant) will increase the number of particles in a unit volume. This will increase the frequency of effective collisions & hence the rate of reaction.

满分回答：

• When the temperature(T) increases, the reactant particles gain kinetic energy(KE).

• The frequency of collision increases and the fraction of particles possessing energy equal or greater than the activation energy increases.

• This results in an increase in the frequency of effective collisions between time.

• Hence, rate of reaction increases.

Note: “frequency of collision & particles with rate of reaction” is required.