Endothermic reaction — Science definition
Defined in 2 courses:
- A reaction that absorbs energy from its surroundings, usually cooling them down. (Physical Science: Matter, Forces & Energy)
- A reaction that absorbs energy from its surroundings; its ΔH is positive and the surroundings cool down. (Physical Science: Chemistry)
Where it is taught
- Endothermic & Exothermic Reactions — Chemistry, Physical Science: Matter, Forces & Energy, Grade 8
- Energy in Chemical Reactions — Chemical Energy & Thermodynamics, Physical Science: Chemistry, Grade 11
In use
An exothermic reaction transfers energy from the reacting system to surroundings; an endothermic reaction takes in energy.
Endothermic & Exothermic Reactions
An endothermic reaction has positive ΔH and, under the appropriate constant-pressure conditions, absorbs heat from surroundings.
Energy in Chemical Reactions
Questions using endothermic reaction
Problem 1
In an endothermic reaction, the energy needed to break bonds is
- less than the energy released forming bonds
- greater than the energy released forming bonds
- exactly equal
- zero
Answer and explanation
greater than the energy released forming bonds
More energy goes into breaking than comes out of forming, so the reaction takes energy in overall.
Problem 2
In an endothermic reaction, the sign of ΔH is…
- negative
- positive
- always zero
- impossible to determine
Answer and explanation
positive
An endothermic reaction absorbs energy into the system, so ΔH is positive.
Taught alongside
- exothermic reaction
- activation energy
- model
- evidence
- system boundary
- assumption
- enthalpy change (ΔH)
- bond energy
- activation energy (Ea)
- specific heat (c)