Meaning & use
exothermic reaction
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Meanings
nouncountablechemistry
A chemical process that gives out energy, usually as heat, so its surroundings become warmer.
Grammar: Countable: several exothermic reactions.
Patterns
- an exothermic reaction between something and something
Burning wood is an exothermic reaction that releases heat and light.
The exothermic reaction made the test tube warm to the touch.
Mixing the acid and the base started an exothermic reaction.
nouncountablechemistrytechnical
A reaction in which the products hold less energy than the starting materials, as shown on an energy diagram.
Grammar: A more technical sense, used in school chemistry.
In an exothermic reaction, the energy of the products is lower than that of the reactants.
The graph shows an exothermic reaction because the line drops.
Students drew an energy profile for the exothermic reaction.
Word forms
| plural | exothermic reactions |
|---|
Common combinations
- release heat in an exothermic reaction
- The mixture released heat in an exothermic reaction.
- strongly exothermic
- The reaction was strongly exothermic and the flask grew hot.
- exothermic reaction between
- An exothermic reaction between iron and oxygen forms rust.
- highly exothermic reaction
- A highly exothermic reaction can cause an explosion.
- start an exothermic reaction
- A tiny spark can start an exothermic reaction.
Synonyms and how they differ
- heat-releasing reaction
- Heat-releasing reaction is the plain-English version, whereas exothermic reaction is the exact scientific term.
- combustion
- Combustion is burning, one kind of exothermic reaction, so it is narrower.
- hot reaction
- Hot reaction is informal and not used in science.
Opposites
Word family
- exothermic adjective
- giving out heat
- endothermic adjective
- taking in heat
- thermal adjective
- relating to heat
- reaction noun
- a chemical change
Commonly confused: exothermic reaction or endothermic reaction?
exothermic reaction vs endothermic reaction
An endothermic reaction absorbs heat and feels cold, while an exothermic reaction releases heat and feels warm.
Practice
When the solid dissolved, the beaker became noticeably warmer, which suggests the change was an ___.
Choose one answer.
A rise in temperature means energy is released, so the change is exothermic. Endothermic reactions absorb heat and make the beaker feel cooler.
Make it your own
Write a sentence using “exothermic reaction”, then check it and compare it with the examples above.