AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Some sports injury packs are based on endothermic reactions.
Full specification wording
Energy transfer during exothermic and endothermic reactions: Some sports injury packs are based on endothermic reactions.
An endothermic reaction takes in energy from its surroundings, so the surroundings cool.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 9 of 12
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
An endothermic reaction takes in energy from its surroundings, so the surroundings cool. A sports injury pack uses this: when the pack is activated, an endothermic reaction absorbs thermal energy from the injured tissue, producing a cold pack that reduces swelling and pain. The reaction mixture and the pack feel cold because energy is transferred from the surroundings to the reacting system. For example, dissolving ammonium nitrate in water in a sealed pack absorbs energy, lowering the temperature. This is the opposite of an exothermic reaction, which releases energy and warms the surroundings. The pack must be designed so the reactants mix only when needed and the cold is safely delivered to the skin without causing ice burns.
What earns the marks
- An endothermic reaction absorbs thermal energy from the surroundings, so the temperature of the surroundings decreases.
- In a sports injury pack, the endothermic process cools the pack, which can be applied to an injury to reduce swelling and pain.
- The reaction mixture feels cold because energy is transferred from the surroundings to the reacting system.
- A named example is dissolving ammonium nitrate in water, which absorbs energy and lowers the temperature.
- The pack is designed so reactants mix only when activated, allowing controlled cooling.
Common mistakes and how to put them right
Thinking that an endothermic reaction makes the pack hot.
Put it right by stating that endothermic reactions absorb energy and cool the surroundings.
Confusing the direction of energy transfer.
Put it right by saying energy moves from the surroundings into the reaction, not from the reaction to the surroundings.
Assuming any cold pack contains a reaction that releases energy.
Put it right by linking the cold sensation to absorption of thermal energy by an endothermic process.
Exam tips
- State clearly that the temperature of the surroundings falls because energy is absorbed.
- Use the phrase 'energy is taken in from the surroundings' rather than vague wording such as 'cold is produced'.
- Link the chemistry to the application: cooling the injury reduces swelling and pain.
Try the lesson
The start of the Energy transfer during exothermic and endothermic reactions: Some sports injury packs are based on endothermic reactions. lesson, made from checked teaching notes for this specification point.
Have a go first
A sports injury pack is placed on a sprained ankle. The pack is based on an endothermic reaction. What happens to the temperature of the pack during the reaction?
Listen
An endothermic reaction takes in energy from its surroundings, so the surroundings cool. A sports injury pack uses this: when the pack is activated, an endothermic reaction absorbs thermal energy from the injured tissue, producing a cold pack that reduces swelling and pain. The reaction mixture and the pack feel cold because energy is transferred from the surroundings to the reacting system. For example, dissolving ammonium nitrate in water in a sealed pack absorbs energy, lowering the temperature. This is the opposite of an exothermic reaction, which releases energy and warms the surroundings. The pack must be designed so the reactants mix only when needed and the cold is safely delivered to the skin without causing ice burns. A strong answer earns marks for these points. An endothermic reaction absorbs thermal energy from the surroundings, so the temperature of the surroundings decreases. In a sports injury pack, the endothermic process cools the pack, which can be applied to an injury to reduce swelling and pain. The reaction mixture feels cold because energy is transferred from the surroundings to the reacting system. A named example is dissolving ammonium nitrate in water, which absorbs energy and lowers the temperature. A common slip: Thinking that an endothermic reaction makes the pack hot. Instead, stating that endothermic reactions absorb energy and cool the surroundings. Exam tip: State clearly that the temperature of the surroundings falls because energy is absorbed.
Key words
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Endothermic reactions
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Energy transfer
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Temperature change of surroundings
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Applications of endothermic reactions
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See every definition
- Endothermic reactions
- Reactions that take in energy from their surroundings, so the surroundings cool.
- Energy transfer
- Energy is transferred from the surroundings to the reacting system, so the reaction mixture feels cold.
- Temperature change of surroundings
- The temperature of the surroundings decreases because an endothermic reaction absorbs thermal energy from them.
- Applications of endothermic reactions
- Sports injury packs use an endothermic reaction to cool an injury and reduce swelling and pain.
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