Kinetic Theory of Matter Investigation

Authors Avatar

The Kinetic Theory of Matter

The main points of the kinetic theory are:

  1. All matter is made up of tiny, invisible, moving particles.
  2. Particles of different substances have different sizes.
  3. Smaller particles move faster than heavier ones at a given temperature.
  4. As the temperature rises, the particles move faster because the particles have more kinetic energy.
  5. In a solid, the particles are a very close together and they can only vibrate about fixed positions.
  6. In a liquid, the particles are a little further apart. They have more energy and they can move around each other.
  7. In a gas, the particles are far apart. They move rapidly and randomly in all the space they can find.

This diagram shows the particles in the three states of matter:

The Collision Theory of Chemical Reactions

A chemical reaction cannot happen unless particles in the reacting substances collide with each other.

There are three main conditions which must be presenting order for a reaction to occur:

  1. The reactant particles must collide.
  2. They must collide at the correct orientation (e.g. a head on collision is better than a glancing blow)
  3. The must collide with a minimum amount of energy, (the activation energy) to allow the rearrangement of atoms; otherwise they simply bounce of each other.

Changing the Rate of a Chemical Reaction

The rate of reaction is only affected if there is a change in the frequency of the collisions, or if the proportion of collisions which are effective (cause a reaction) changes.

There are six main ways to increase the rate of a chemical reaction.

1. Reducing the size of the particles of a solid reactant.

This increases the surface area of the solid reactant and therefore the number of particles exposed to react. This means there is an increase in the frequency of the collisions.

2. Increasing the concentration of a solution.

This means there are more reactant particles per cm², therefore the frequency of collisions increases.

3. Increasing the temperature of the reaction.

Increasing the temperature gives particles more kinetic energy. Faster moving particles collide more often and a higher proportion of the collisions will exceed the activation energy of the reaction. Usually a 10°C increase will double the reaction rate.

4. Increasing the pressure of reacting gasses.

Increasing the pressure of a gas means there are more molecules per cm³, and therefore more frequent collisions.

5. Shining light on photosensitive reactions.

In photosensitive reactions sunlight provides the energy for the reaction. So more light means more particles possess sufficient energy to overcome the activation energy when they collide.

6. Adding a suitable catalyst.

Join now!

Catalysts are specific for particular reactions. They work by providing an alternative route for the reaction which has a lower activation energy. Therefore a higher proportion of the collisions are effective. Catalysts can also be used to slow down reactions.


  • Measure 100 ml of hydrochloric acid into a conical flask.
  • Half fill the container with water.
  • Fill the measuring cylinder with water and turn it up-side down in the container without letting any gas into the measuring cylinder.
  • Place the ...

This is a preview of the whole essay