Changes in enthalpy occur whenever heat is released or absorbed in a physical, chemical, or nuclear change. Enthalpy change can be measured in J or kJ. Which term describes this heat-driven energy change?

Changes in enthalpy occur whenever heat is released or absorbed in a physical, chemical, or nuclear change. Enthalpy change can be measured in J or kJ. Which term describes this heat-driven energy change?

• A. Enthalpy Change
• B. Heat Transfer
• C. Entropy Change
• D. Internal Energy Change

Answer: (A)

Enthalpy change is the heat content change of a system as it absorbs or releases heat. It’s measured in joules or kilojoules, and at constant pressure the heat exchanged with the surroundings equals this enthalpy change, which is why it’s the term that best describes a heat-driven energy change. This differs from heat transfer, which is the process of energy moving due to a temperature difference, from entropy change, which relates to disorder, and from internal energy change, which includes all forms of energy inside the system (and is related to enthalpy by ΔH = ΔU + Δ(PV)).

Enthalpy change is the heat content change of a system as it absorbs or releases heat. It’s measured in joules or kilojoules, and at constant pressure the heat exchanged with the surroundings equals this enthalpy change, which is why it’s the term that best describes a heat-driven energy change. This differs from heat transfer, which is the process of energy moving due to a temperature difference, from entropy change, which relates to disorder, and from internal energy change, which includes all forms of energy inside the system (and is related to enthalpy by ΔH = ΔU + Δ(PV)).