Rates of
Chemical Reactions

Back

Home

Fast and Slow Chemical reactions

The speed at which chemicals react is called the rate of reaction

Quick chemical reactions might be explosions and combustion
Slow ones might be rust and fermentation.

Controlling the Rate of Reaction

Rates can be changed by a number of different variables

• Temperature
• concentration of the reactants
• surface areaarea
• Agitation ( stirring)
• Catalysts

Temperature

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

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

Lowering the temperature can reduce the rate of reaction.

Concentration

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

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

Agitation

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

Surface Area of Reactants

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

Catalyst

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

• Reducing the amount of energy needed
• Make it easier for reactants to collide and form products

Enzymes

Enzymes are biological catalysts catalysts.

Enzymes make your body work right.  You have 1000's of enzymes in your body that do only one job.

The enzyme in your mouth that breaks down sugar is amylase

Summary Video