alleryStart learning →In thermodynamic terms, how is heat energy defined?
AThe energy stored in the bonds of the reactants
BThe energy transferred between systems that does no work
CThe energy needed to reach the transition state
DThe energy released when a phosphate bond breaks
Answer & Solution
Correct answer: B. The energy transferred between systems that does no work
1. Thermodynamically, heat energy is the energy transferred from one system to another that is not doing work.
2. When an airplane flies, some energy is lost as heat energy due to friction with the surrounding air.
3. That friction heats the air by temporarily increasing the speed of air molecules, which is energy that performed no useful work.
4. Total bond energy of reactants or products is a separate use of the same phrase and is not the thermodynamic definition here.
5. Energy needed to reach the transition state is the activation energy, a distinct quantity.
6. Energy released by breaking a phosphate bond is a specific chemical case rather than a general definition.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 6 "Metabolism", section 6.3 The Laws of Thermodynamics_
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