Exothermic and Endothermic Reactions
Exothermic reactions release heat to the surroundings, while endothermic reactions absorb heat from them.
▶ Interact
Play with the controls to see the idea in action.
📘 Learn
Exothermic reactions release heat to the surroundings, while endothermic reactions absorb heat from them.
- Combustion is exothermic
- Thermal decomposition is endothermic
- Temperature rises in exothermic reactions
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Exothermic and Endothermic Reactions?
Within Chemistry, which covers atoms, bonding, reactions, the periodic table, organic chemistry and the chemistry of everyday life, this topic explains Exothermic and Endothermic Reactions. Chemistry links what you can see in the lab to the particles and bonds behind it, so each topic here shows that link in a model.
Check that you can explain Exothermic and Endothermic Reactions in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Exothermic and Endothermic Reactions helps you explain why substances behave as they do, from cleaning products and food to medicines.
Exothermic and Endothermic Reactions in detail
An exothermic reaction transfers energy to the surroundings, so the temperature of the surroundings rises. Examples are combustion, neutralisation and respiration. Hand warmers and self-heating cans use them.
An endothermic reaction takes in energy from the surroundings, so the temperature falls, as in thermal decomposition, photosynthesis and dissolving ammonium nitrate, which is used in cold packs. Temperature changes are measured with a thermometer in an insulated container. Many reactions need energy to start, but they can still be exothermic overall.
How the interactive helps you understand Exothermic and Endothermic Reactions
Watch the energy stores in the interactive. Use any sliders or buttons it offers to change the values and see how the energy stores responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Exothermic and Endothermic Reactions.
Real-life uses and examples
- Read a chemical equation or diagram and work out what Exothermic and Endothermic Reactions shows.
- Explain Exothermic and Endothermic Reactions in an exam by linking the particles involved to what you observe.
- Use Exothermic and Endothermic Reactions to explain what happens in a lab experiment and why.
Common mistakes to avoid
- Describing what happens without explaining the particles or bonds involved.
- Mixing up the names of substances or ions when you describe Exothermic and Endothermic Reactions.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Exothermic and Endothermic Reactions
What is Exothermic and Endothermic Reactions?
Exothermic reactions release heat to the surroundings, while endothermic reactions absorb heat from them.
What are the most important points about Exothermic and Endothermic Reactions?
The main points are: Combustion is exothermic; Thermal decomposition is endothermic; Temperature rises in exothermic reactions.
Why is Exothermic and Endothermic Reactions useful?
Understanding Exothermic and Endothermic Reactions helps you explain why substances behave as they do, from cleaning products and food to medicines.
How can I practise Exothermic and Endothermic Reactions?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Exothermic and Endothermic Reactions?
Related topics in Chemistry include Reversible Reactions, Fertilisers and Agriculture, Alkanes.