To study how concentration affects the rate of a reaction.

Essay by gr00uch March 2004

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The Collision Theory

For particles to react, they must collide. They must also collide with enough energy for a reaction to take place. The energy created is called activation energy. The more often and faster the chemicals collide, the stronger the reaction.

Rate of Reaction

The rate of a reaction depends on four things:

*Temperature - When the temperature increases the particles start to all move quicker. This means that there will be more collisions and more energy will be given out.

*Concentration - If a solution is highly concentrated it means that there are a lot of particles that can collide. This means that there is more chance that a reaction will occur.

*Catalyst - A catalyst gives the reacting particles a surface to stick to and still collide. This lowers the activation energy, making it easier for the reaction to take place. A catalyst does not take place in the reaction itself.

*Size of particles (surface area) - A few small fragments of a substance will have a larger surface area than one large piece because the fragments will have more area for the solution to work on.

There are three ways you can measure the speed of a reaction.

*Precipitation - This is when the product of the reaction is a precipitate which clouds the solution

*Change in mass - If the reaction produces a gas, the experiment can be carried out on a mass balance. As the gas is released, the change in mass can be measured easily.

*Volume of gas given off - As gas is given out, a gas syringe measures the total amount released

Experiment write up


To plan and carry out an investigation that shows how concentration affects the rate of a reaction.

Key factors

I will only change the...