Enthalpy vs. Internal Energy: What's the Difference?
Edited by Sawaira Riaz || By Sumera Saeed || Updated on October 25, 2023
Enthalpy represents the total heat content of a system, while internal energy is the energy associated with the random movement of molecules.
Key Differences
Enthalpy and internal energy are fundamental concepts in thermodynamics, vital in understanding energy changes in systems.
Sumera Saeed
Oct 25, 2023
It includes not just the energy of the molecules moving and vibrating, but also the energy involved in the breaking and forming of chemical bonds.
Sumera Saeed
Oct 25, 2023
In contrast, internal energy, focuses primarily on the energy associated with the random motion of molecules, including translational, rotational, and vibrational energies. It does not account for the energy involved in phase transitions or the energy required for the system to expand or contract against its surroundings.
Sumera Saeed
Oct 25, 2023
One key distinction between enthalpy and internal energy lies in how they relate to heat and work in a system.
Sumera Saeed
Oct 25, 2023
Enthalpy is especially useful when discussing processes at constant pressure, like most chemical reactions. On the other hand, internal energy provides a more generalized picture of energy changes in a system, irrespective of external pressures or volumes. It’s important to remember that neither enthalpy nor internal energy can be measured directly; only their changes can be observed.
Sumera Saeed
Oct 25, 2023
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Comparison Chart
Definition
Total energy content of a system
Energy related to random motion of molecules
Sumera Saeed
Oct 25, 2023
Components
Includes chemical bond energies
Excludes bond formation or breaking energies
Sumera Saeed
Oct 25, 2023
Relation to Heat and Work
Change equals heat transfer at constant pressure
Change relates to both heat and work
Sumera Saeed
Oct 25, 2023
Typical Uses
Processes at constant pressure like chemical reactions
General energy changes, irrespective of pressure or volume
Sumera Saeed
Oct 25, 2023
Direct Measurement
Neither can be measured directly, only changes are observed
Neither can be measured directly, only changes are observed
Janet White
Oct 25, 2023
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Enthalpy and Internal Energy Definitions
Enthalpy
The total heat content of a system.
During an exothermic reaction, the enthalpy of the system decreases.
Sara Rehman
Oct 25, 2023
Internal Energy
Energy due to the random motion of molecules.
Rising temperature increases the internal energy of a system.
Sawaira Riaz
Oct 25, 2023
Enthalpy
Sum of internal energy and product of pressure and volume.
Enthalpy is used in calorimetry to measure heat flow.
Janet White
Oct 25, 2023
Internal Energy
Sum of all microscopic forms of energy in a system.
The internal energy decreases in an exothermic process.
Sumera Saeed
Oct 25, 2023
Enthalpy
Energy measure that combines internal energy and work.
The change in enthalpy helps us determine the heat of a reaction.
Harlon Moss
Oct 25, 2023
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Internal Energy
A state function reflecting energy changes in a system.
The first law of thermodynamics describes how internal energy varies with heat and work.
Janet White
Oct 25, 2023
Enthalpy
Represents heat flow in processes at constant pressure.
For many chemical reactions, the enthalpy change is a crucial parameter.
Sawaira Riaz
Oct 25, 2023
Internal Energy
Total energy stored within the boundaries of a system.
When a gas is compressed, its internal energy increases due to molecular interactions.
Aimie Carlson
Oct 25, 2023
Enthalpy
Thermodynamic potential measuring total energy of a system.
Enthalpy changes give insights into the energy changes during phase transitions.
Sara Rehman
Oct 25, 2023
Internal Energy
Related to the kinetic and potential energies of particles.
Molecular vibrations and rotations contribute to the system's internal energy.
Sumera Saeed
Oct 25, 2023
Enthalpy
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.
Sumera Saeed
Mar 02, 2022
Enthalpy
A measure of the heat content of a chemical or physical system.
, where H is enthalpy, U is internal energy, p is pressure, and V is volume.
Sumera Saeed
Mar 02, 2022
Enthalpy
(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
Sumera Saeed
Mar 02, 2022
FAQs
Is enthalpy always related to heat?
At constant pressure, the change in enthalpy equals the heat transferred.
Sawaira Riaz
Oct 25, 2023
What contributes to the internal energy of a system?
It includes translational, rotational, and vibrational energies of molecules.
Sumera Saeed
Oct 25, 2023
Does the internal energy change with temperature?
Yes, as temperature increases, internal energy typically rises.
Aimie Carlson
Oct 25, 2023
How is enthalpy related to the internal energy?
Enthalpy is the sum of internal energy and the product of pressure and volume.
Sumera Saeed
Oct 25, 2023
Can we directly measure enthalpy or internal energy?
No, only their changes can be measured or observed.
Sumera Saeed
Oct 25, 2023
When is enthalpy most commonly used?
For processes at constant pressure, especially in chemical reactions.
Harlon Moss
Oct 25, 2023
What does a negative change in enthalpy indicate?
It indicates an exothermic process or reaction.
Sara Rehman
Oct 25, 2023
Can the internal energy determine if a reaction is spontaneous?
No, spontaneity is determined by the Gibbs free energy, not just internal energy.
Aimie Carlson
Oct 25, 2023
Why is enthalpy useful in understanding chemical reactions?
It provides insights into the heat flow and energy changes in reactions.
Sumera Saeed
Oct 25, 2023
What factors affect the internal energy of a system?
Temperature, volume, and number of particles are some factors.
Aimie Carlson
Oct 25, 2023
Can a system have zero internal energy?
Theoretically, at absolute zero temperature, a system would have minimal internal energy.
Aimie Carlson
Oct 25, 2023
Is the internal energy a state function?
Yes, it only depends on the current state, not the path taken to reach it.
Sara Rehman
Oct 25, 2023
Are enthalpy and entropy related?
While both are state functions, they represent different thermodynamic quantities.
Sumera Saeed
Oct 25, 2023
Do all reactions involve a change in enthalpy?
Most reactions involve enthalpy changes, though some might have negligible changes.
Harlon Moss
Oct 25, 2023
Can the internal energy be negative?
Internal energy is always a positive quantity, but its change can be negative.
Aimie Carlson
Oct 25, 2023
What is the relation between internal energy and the first law of thermodynamics?
The first law describes how internal energy changes with heat and work.
Sumera Saeed
Oct 25, 2023
Does increasing volume always increase internal energy?
Not necessarily; the relationship depends on the nature of the system and process.
Janet White
Oct 25, 2023
Why is the change in enthalpy important in chemistry?
It helps determine if reactions are endothermic or exothermic.
Sara Rehman
Oct 25, 2023
How is enthalpy used in calorimetry?
Enthalpy changes represent the heat flow measured in calorimetry.
Sara Rehman
Oct 25, 2023
About Author
Written by
Sumera SaeedSumera is an experienced content writer and editor with a niche in comparative analysis. At Diffeence Wiki, she crafts clear and unbiased comparisons to guide readers in making informed decisions. With a dedication to thorough research and quality, Sumera's work stands out in the digital realm. Off the clock, she enjoys reading and exploring diverse cultures.
Edited by
Sawaira RiazSawaira is a dedicated content editor at difference.wiki, where she meticulously refines articles to ensure clarity and accuracy. With a keen eye for detail, she upholds the site's commitment to delivering insightful and precise content.
