Chemistry A-Level
Sign convention
What Sign convention means in Chemistry A-Level, as defined for OCR.
Definition of Sign convention
Check what you remember
Read the wording for your board, then hide it and explain Sign convention in your own words. Rough notes are fine. This is a self-check, with no mark or grade.
Reference: OCR
A convention fixed relative to the system, so the sign of ∆H follows the direction of energy leaving or entering the system rather than the size of the change.
Topics that use Sign convention
- 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 convention 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.
Start free
All Chemistry A-Level termsA week of Premium from your first lesson · Then the free plan continues · No card, no charge