5.1.2

Exothermic & Endothermic Reactions

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Exothermic Reactions

In exothermic reactions, energy from the reacting chemicals is transferred to the surroundings. This often leads to an increase in temperature. Examples include:

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Hand warmers

  • Disposable hand warmers use the energy released by iron oxidation.
  • Reusable hand warmers source their energy from the crystallisation of salt solutions. Boiling the pack re-dissolves the crystals, so that it's ready to be activated once more.

Endothermic Reactions

In endothermic reactions, energy from the surroundings is transferred to the reacting chemicals. This decreases the temperature of the surroundings. Examples include:

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Sports injury packs

  • When squeezed forcefully, ammonium nitrate and water mix in the pack, resulting in instant cooling.
  • The speed of this reaction makes these packs ideal for scenarios when ice is not immediately available.

Jump to other topics

1Atomic Structure

2Chemical Bonding

3Quantitative Chemistry

4Chemical Changes

5Energy Changes

6The Rate & Extent of Chemical Change

7Organic Chemistry

8Chemical Analysis

9Chemistry of the Atmosphere

10Using Resources

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