Collision Theory and Energy Transfer

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Collision Theory

There are four factors that increase the number of collisions of particles in an experiment...

1) Higher Temperature

  • At a higher themperature, the particled move more quickly as they have more energy.
  • This causes them to collide more frequently.

2) Higher Concentration or Pressure

  • If a solution is more concentrated, there are more particles, meaning they are more likely to collide. The same principle works for gases under pressure.

3) Larger Surface Area

  • Having a larger surface area means that there is a greater area for the paricles to collide with.

4) Catalysts

  • They increase the number of collisions by lowering the activation energy.
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Energy Transfer in Reactions

Bond Breaking ---> Energy must be supplied for the bonds in molecules to break. This means that breaking bonds is endothermic

Bond Forming ---> Energy is given out from the molecule when a bond is formed, so this process is exothermic.

Exothermic Reactions:

  • In an exothermic reaction, energy is released because more bonds are made than broken.
  • The temperature of the surroundings will rise because energy is given out.

Endothermic Reactions:

  • In an endothermic reaction, energy is taken in because the energy needed to break bonds is greater than the energy needed to make them.
  • The surrounding temperature will fall because the energy is taken in.

The change in energy is called an enthalpy change and is measured in /\H (kJ/mol).

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