To investigate the effect of temperature on the rate of reaction

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Chemistry Coursework        Haaziq Farook    11o

GCSE Triple Science Chemistry:

Rate of Reaction

Aim: To investigate the effect of temperature on the rate of reaction

Define: Chemical Reaction

A chemical reaction is a process that results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants. Chemical reactions are characterised by a chemical change, and they yield one or more products which are, in general, different from the reactants. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions.

[Source: Wikipedia]

Collision Theory – Energy of the Collision

Activation Energy

Regardless of whether the species are orientated correctly, a reaction will still not fail to occur unless the particles collide with a certain minimum energy called the activation energy of the reaction.

Activation energy is the minimum energy required before a reaction can occur. This can be shown on an energy profile for the reaction. For a simple over-all exothermic reaction, the energy profile looks like this:

If the particles collide with less energy than the activation energy, nothing significant happens; they bounce apart, Activation energy serves as a barrier to the reaction. Only those collisions which have energies equal to or greater than the activation energy result in a reaction.

Any chemical reaction results in the breaking of some bonds (needing energy) and the making of new ones (releasing energy). Clearly, some bonds have to be broken before new ones can be made. Activation energy is involved in breaking some of the original bonds.

Where collisions are relatively gentle, there isn’t enough energy available to start the bond-breaking process, and so the particles do not react.

Due to the key role of activation energy in deciding whether a collision will result in a reaction, it would obviously be useful to know what sort of proportion of the particles present have high enough energies to react when they collide.

In any state, the particles present will have a very wide range of energies. For gases, this can be shown on a graph called the Maxwell-Boltzmann Distribution which is a plot of the number of particles having a particular energy.

This graph below only applies to gases, but the conclusions that we can draw from it can also be applied to reactions involving the liquids.

The area under the curve is a measure of the total number of particles present.

We see that the vast majority of the particles don’t have enough energy to react when they collide. To enable them to react we either have to change the shape of the curve, or move the activation energy further to the left.

I predict that, as the temperature increases, the rate of reaction will become faster and as a result increase. Increasing the temperature would also give the particles more kinetic energy, making them vibrate more and increasing the likelihood of colliding. It also increases the chance that the collisions will be successful because they have more energy than what is needed for activation of the reaction. This is because particles have more kinetic energy, overcoming the energy barrier hence giving more particles more energy than what is needed for activation energy.  I expect that, for instance, when the temperature is 200C, the rate of reaction will be approximately 1 Vm/sec-1; and when the temperature is doubled to 40, the rate will also double.

In my experiment, I will be investigating the effect of temperature on the rate of reaction between marble chips and hydrochloric acid. So to summarise my prediction; I think that as the temperature increases, the rate of reaction between the marble and acid will become faster.

Factors that affect the rate of reaction (aside from Temperature)

  • Concentration of reactants
  • Catalysts
  • Surface area of a solid reactant

Concentration of Reactants

Increasing the concentration of the reactants will increase the frequency of collisions between the two reactants. The molecules in the reaction mixture have a range of energy levels. Therefore, increasing the concentration would increase the kinetic energy in the particles; resulting in a greater chance of colliding, and also an increased likelihood of these collisions being successful. When collisions occur, they do not always result in a reaction. If the two colliding molecules have sufficient energy they will react. Hence, if the concentration of the reactant is increased, there is a much higher chance that the two colliding molecules have that sufficient energy (activation energy).


Catalysts speed up chemical reactions. Only very small quantities of the catalyst are needed to result in a significant change in the rate of the reaction. This means that using a catalyst lowers the activation energy; therefore meaning that a greater number of molecules have energy that is more than what is needed for activation.

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Surface area of a solid reactant

The surface area of the solid reactant can affect the rate of reaction. This is because the two types of molecule can only bump into each other on the surface of the solid. Therefore, simply, the larger the surface area of the solid, the faster the reaction will be.



My preliminary consists of me measuring ...

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This is a very well written report. The experimental method is evaluated with preliminary tests used to refine the experimental method. The data is robust and reliable. The main limitation is the lack of any graphs of the experimental data collected. There are specific strengths and limitations suggested throughout.