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Energy vs. Enthalpy: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on January 22, 2024
Energy is the capacity to do work or produce heat, whereas enthalpy is a thermodynamic property representing heat content under constant pressure.

Key Differences

Energy is a fundamental concept in physics, representing the capacity to do work. Enthalpy, a specific form of energy, reflects the total heat content of a system at constant pressure.
Energy exists in various forms like kinetic, potential, and thermal. Enthalpy specifically measures the internal energy plus the product of pressure and volume of a system.
The law of conservation of energy states that energy cannot be created or destroyed. In thermodynamics, enthalpy change indicates the heat absorbed or released in a process at constant pressure.
Energy is a more general concept and is not limited to thermodynamic systems. Enthalpy is a thermodynamic property, crucial in understanding energy changes in chemical reactions.
In practical applications, energy is considered in contexts like mechanical work and electricity. Enthalpy is particularly important in chemistry and chemical engineering for calculating heat changes.

Comparison Chart


Capacity to do work or produce heat
Total heat content of a system at constant pressure


Kinetic, potential, thermal, etc.
Internal energy plus the product of pressure and volume

Conservation Law

Cannot be created or destroyed
Change represents heat absorbed or released at constant pressure


General concept in physics and engineering
Specific to thermodynamic systems


Broad, including mechanics, electricity, etc.
Focused on chemistry and chemical engineering

Energy and Enthalpy Definitions


It exists in forms like kinetic and potential energy.
The energy stored in a compressed spring is potential energy.


Enthalpy is a measure of total heat content in a system.
The enthalpy change in a reaction helps in understanding its energy dynamics.


Energy is the capacity to perform work.
The wind turbine converts kinetic energy into electrical energy.


It includes internal energy and the product of pressure and volume.
In a constant pressure system, enthalpy change indicates heat exchange.


Energy transfer is central to all physical processes.
Photosynthesis is a process of converting solar energy into chemical energy.


It helps in understanding energy changes during phase transitions.
The enthalpy of vaporization quantifies the energy required to vaporize a liquid.


Energy is a key concept in both physics and engineering.
Engineers calculate energy efficiency to design better machines.


Enthalpy is used to calculate heat changes in chemical reactions.
The enthalpy of combustion determines the energy released in burning fuels.


Energy conservation is a fundamental principle in physics.
In an isolated system, the total energy remains constant.


Enthalpy is crucial in thermodynamic calculations.
Calculating enthalpy changes is fundamental in chemical engineering.


The capacity for work or vigorous activity
Who has the energy to climb that trail?.


Symbol H A thermodynamic function of a system, equivalent to the sum of the internal energy of the system plus the product of its volume multiplied by the pressure exerted on it by its surroundings.


Also energies Exertion of vigor or power
A project requiring a great deal of time and energy.
Devoted her energies to writing songs.


A measure of the heat content of a chemical or physical system.
H = U + p V , where H is enthalpy, U is internal energy, p is pressure, and V is volume.


(thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure;
Enthalpy is the amount of energy in a system capable of doing mechanical work


What is energy fundamentally?

Energy is the capacity to do work or transfer heat.

How is enthalpy used in chemistry?

Enthalpy is used to calculate heat changes in chemical reactions.

Is enthalpy conserved like energy?

No, enthalpy is not conserved; it changes during processes.

What are common forms of energy?

Kinetic, potential, and thermal energy are common forms.

How is energy measured?

Energy is measured in joules, calories, or kilowatt-hours.

What is standard enthalpy change?

It's the enthalpy change when reactants and products are at standard conditions.

Is energy transfer always efficient?

No, there can be losses, such as heat loss, making transfers less efficient.

Can energy be destroyed?

No, according to the law of conservation of energy, it cannot be destroyed.

What is the enthalpy of formation?

It's the change in enthalpy when one mole of a compound forms from its elements.

Can energy be converted between forms?

Yes, energy can be converted from one form to another.

Is enthalpy a state function?

Yes, enthalpy is a state function; it depends only on the state of the system.

What does a change in enthalpy indicate?

It indicates the amount of heat absorbed or released at constant pressure.

What is thermal energy?

Thermal energy is the energy that comes from the temperature of matter.

How does energy relate to motion?

Kinetic energy is the energy an object possesses due to its motion.

What is enthalpy used for in engineering?

It's used in heat exchanger design and thermodynamic cycle analysis.

What role does energy play in ecosystems?

Energy flow is essential in ecosystem dynamics, like in food chains.

How does energy affect climate?

Solar energy drives climate systems and weather patterns on Earth.

What is the enthalpy of combustion?

It's the heat change when one mole of a substance burns completely.

How is enthalpy related to phase changes?

Enthalpy changes occur during phase changes, like melting or vaporization.

Can enthalpy be negative?

Yes, negative enthalpy change indicates heat release to the surroundings.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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