When talking about the different factors that affect the rate of a chemical reaction, chemists will often use a simplification known as the 'colliding particle model' to explain the impact of different factors on rate. In this model the chemical compounds that are reacting are described as solid particles, that collide with each other to cause a reaction to occur. However, not every collision will lead to a successful reaction. For a reaction to occur there has to be a collision between the correct particles, the particles need to have the right amount of speed (a.k.a kinetic energy) and the collision has to happen under the correct angle. Using these assumptions, we can explain the impact of the different factors on the rate of reaction
An increase in the concentration of a certain reactant means that there will be more of that particle present in the same volume. This will naturally lead to more collisions between particles, leading to more effective collisions and therefore an increase in the rate.
The distribution degree of a certain compound refers to the amount of surface area of the compound relative to the amount of compound present. Think about aluminium for example. You could have a block of aluminium, but this block has a pretty small surface area compared to the amount of aluminium present in the block. If you break the block down into thin sheets of aluminium, the surface area of the aluminium is much larger, even though we have the same amount of compound. It is pretty self-explanatory that a chemical reaction between the aluminium and another compound can only occur on the surface of the aluminium, as that is the only place where different kinds of particles can come together to collide and undergo a reaction. Therefore, increasing the degree of distribution will lead to more collisions (cause of a relatively larger surface area), and subsequently lead to a higher rate.
As you know, temperature is effectively a measure of the average kinetic energy of the molecules in a certain compound. An increase in temperature therefore means that the average kinetic energy of particles increases. This will lead to more collisions, as the particles move around more vividly, but also means that the collisions will happen with more speed, making them more likely to be effective collisions. Increasing the temperature of your reaction vessel can therefore be a very effective way to increase the rate of your reaction. Though you should watch out for equilibrium reactions, as an increase in temperature could lead to a new equilibrium state in which the reactants are much more abundant than before, meaning you increased the rate of reaction, but decreased the yield of your reaction.
A catalyst is a compound that is used to aid a certain chemical reaction, but is not used up in that reaction. A catalyst will lead to a decrease in the activation energy for a reaction, meaning that lower energy collisions could all of a sudden become effective collisions when aided by a catalyst. The use of a catalyst can therefore lead to drastic increases in reaction rate, or make reactions possible under conditions where they would normally never occur.
Written by Imre Bekkering