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Rates of reaction


Changes in matter ] Importance of chemical reactions ] Chemical Reactions ] On-line practice ]

‘Rate of reaction’ means ‘how fast is the reaction’. 

It can be measured as 

  • the 'rate of formation of product

  • the 'rate of disappearance of reactant'.

Examples :

  • Rusting is a ‘slow’ reaction, 

  • Weathering of rocks is a very slow reaction,

  • Fermentation of sugar to alcohol is quite slow but you can see the carbon dioxide bubbles forming in the 'froth'!

  • A ‘fast’ reaction would be magnesium dissolving in hydrochloric acid,

  • An explosion and burning/combustion reactions would be described as ‘very fast’

A reaction will continue until one of the reactants is used up.

To measure the ‘speed’ or ‘rate’ of a reaction depends on what the reaction is, and can what is formed be measured as the reaction proceeds.

Methods to find out reaction speeds :

  • measure time for a reaction to be completed
  • measure amounts of product produced in a period of time
  • measure amounts of reactant remaining in a period of time


Exothermic and endothermic changes ] Energy level diagrams ] Activation energy ] [ Rates of reaction ] Factors affecting rate of reaction ]