Rates of
Chemical Reactions

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Fast and Slow Chemical reactions

The speed at which chemicals react is called the

Quick chemical reactions might be and
Slow ones might be and .

Controlling the Rate of Reaction

Rates can be changed by a number of different variables

  • Temperature
  • of the reactants
  • area
  • Agitation ()
  • Catalysts


temperature will normally increase the rate of the reaction for two reasons

  • the particles thus increasing collisions
  • Particles have more to break bonds when they do collide.

Lowering the temperature can reduce the of reaction.


Increasing the of the reactants increases the rate of reaction because there are more particles to .

Reducing the concentration can act to a process.  Eg, reducing the amount of oxygen (air) can cause a fire to go slow of go out.


Stirring adds energy to the molecules and so they more often.

Surface Area of Reactants

By increasing the amount of space a reaction can take place on causes a reaction to.


A is a chemical that speeds up a reaction without actually itself
They work by

  • Reducing the amount of needed
  • Make it easier for reactants to


are biological catalysts catalysts.

Enzymes make your body work right.  You have enzymes in your body that do only job.

The enzyme in your mouth that breaks down sugar is

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