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Controlling chemical reactions - OCR GatewayRates and temperature

The greater the frequency of successful collisions between reactant particles, the greater the reaction rate. Temperature, concentration, pressure and the use of catalysts affect reaction rate.

Part of Chemistry (Single Science)Monitoring and controlling chemical reactions

Rates and temperature

The greater the rate or frequency of , the greater the rate of reaction. If the of the reaction mixture is increased:

  • move more quickly
  • the of the particles increases
  • the frequency of successful collisions between reactant particles increases
  • the proportion of collisions which are successful also increases
  • the rate of reaction increases

Question

Explain what is meant by a 鈥榮uccessful鈥 collision.

Graphs

The rates of two or more reactions can be compared using a graph of or of formed against time. The graph shows this for two reactions.

Graph of total mass of product against time from start of reaction, for high and low temperature.
Figure caption,
Comparing reactions of different temperatures

The of the line is equal to the rate of reaction. The faster reaction at the higher temperature:

  • gives a steeper line
  • finishes sooner