See what effect changing the temperature has on the rate of reaction between sodium thiosulphate and hydrochloric acid.

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Gcse chemistry coursework

Background

Collisions and reactions

For a chemical reaction to occur, reactant particles must collide.

  • Increasing the temperature of a reaction increases the rate of a reaction. At the higher temperatures reactant particles move faster and collide more often and more violently.
  • Increasing the concentration of reactants increases the rate of a reaction. This is because there are more particles in the same volume so more collisions are possible every second.
  • Breaking up solids into smaller pieces increases reaction rate because this increases the total surface area. Increasing the surface area must increase the number of particles of the solid in contact with the other reactant in solution.
  • Using a catalyst increases the rate of a reaction. Catalysts are not used up in a reaction

Activation energy

For a chemical reaction to take place, some bonds in the reactants must be broken. The colliding particles must have enough energy to break these bonds. This minimum amount of energy is called the activation energy. Only the very fastest moving particles have enough energy to break bonds.

In gases, liquids and in solution, the particles move at a range of speeds. Some are moving very slowly and others are moving very fast. To react, particles must collide with enough energy and in the correct orientation for bonds to be broken.

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In summary.

Activation energy 

The minimum energy needed to break bonds in the reactants for a reaction to occur

Catalyst 

A substance which increases the rate of reaction but is not used up in the reaction.

Gas pressure 

The pressure due to gas molecules colliding with the walls of the container they are placed in - each molecule hits a tiny area of the wall with a force

Rates of reaction.

A rate of reaction is the rate or speed at which a reaction takes place.

Reactions can only occur when atoms or molecules hit each other physically. ...

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