Sign conventions
What Sign conventions means in Chemistry A-Level, as defined for OCR.
Definitions of Sign conventions
Exam boards and our study guides word this term in slightly different ways. Learn the version your board uses.
Check what you remember
Read the wording for your board, then hide it and explain Sign conventions in your own words. Rough notes are fine. This is a self-check, with no mark or grade.
Reference: OCR
Reversing the equation reverses the sign of ∆rH, since exothermic becomes endothermic and vice versa.
The sign of a value is reversed when the cycle requires the step to run in the opposite direction.
Topics that use Sign conventions
- Enthalpy changes (OCR A-Level)
Related terms
- ∆H of combustion
- ∆H of formation
- Activation energy
- Approximate estimate
- Average bond enthalpy
- Averaging over gaseous compounds
- Bond breaking and bond making
- Bond enthalpy
Using Sign conventions in the exam
Check the command word and mark scheme for your exact question. After comparing your explanation with the reference, use the term in an answer on the linked topic. This practice does not predict an exam mark.
Practise Chemistry questions
Create a free account to answer exam-style questions on this topic and get feedback on your answers.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge