Which property is used to describe both the amount of heat transferred and the temperature at which it is transferred?

Which property is used to describe both the amount of heat transferred and the temperature at which it is transferred?

• A. Entropy
• B. Internal Energy
• C. Pressure
• D. Volume

Answer: (A)

Entropy is the quantity that ties together how much heat is transferred and the temperature at which it occurs. For a reversible heat transfer, the infinitesimal amount of heat added is δQ_rev = T dS. This means the change in entropy is δS = δQ_rev / T, so the total heat transferred during a reversible process is Q_rev = ∫ T dS. In other words, entropy measures the amount of heat transferred per unit temperature and directly relates to the temperature at which that transfer happens. Internal energy describes the system’s energy content, not the heat transfer amount per temperature, while pressure and volume are state properties that don’t quantify heat transfer.

Entropy is the quantity that ties together how much heat is transferred and the temperature at which it occurs. For a reversible heat transfer, the infinitesimal amount of heat added is δQ_rev = T dS. This means the change in entropy is δS = δQ_rev / T, so the total heat transferred during a reversible process is Q_rev = ∫ T dS. In other words, entropy measures the amount of heat transferred per unit temperature and directly relates to the temperature at which that transfer happens. Internal energy describes the system’s energy content, not the heat transfer amount per temperature, while pressure and volume are state properties that don’t quantify heat transfer.