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. (如果是increase particle size 就相反哦)
Concentration/Pressure of liquid & gaseous reactants
重点: 在看这种volume-time diagram的时候，如果concentration or pressure of reactants increases by twice但是volume of reactants没有变，volume of products also increases by twice。
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.
因为HCl是limiting agent, 但是图上的volume of CO2 没有变化, 所以concentration of HCl也不变, 也就是1.00mol dm-3。那么唯一可以的就是decrease size of lumps, 所以答案选C。
• 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（Ea）increases.
• This results in an increase in the frequency of effective collisions between time.
• Hence, rate of reaction increases.
当我们想答案时, 只需要想 T ↑ → KE ↑ → frequency of collision & particles with E≥Ea↑ rate of reaction ↑ 就好啦！
Using a Maxwell Boltzmann distribution curve, explain how increasing the temperature increases the rate of reaction.
说到catalyst， IB真的非常喜欢考, 所以定义必须得熟记于心:
A catalyst is a substance that increases the rate of a chemical reaction without being chemically changed at the end of reaction.
那么catalyst到底改变了什么？为什么它可以加速reaction？答案就是activation energy is decreased! 一般有两种常考的图来表现：
Energy profile diagram
Maxwell-Boltzmann energy distribution curve
满分回答：Adding a catalyst decreases the activation energy of a reaction. Hence, the fraction of particles possessing energy equal or greater than the activation energy （Ea）increases. This results in an increase in the frequency of effective collisions between time.