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Guilherme Mazui

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What is the Difference Between Energy and Enthalpy?

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The main difference between energy and enthalpy lies in their definitions and how they are used in thermodynamics:

  1. Energy: Energy is the ability to do work or effect change in a system. In thermodynamics, internal energy is the total energy (potential or kinetic) in a thermodynamic system. It is measured in joules.
  2. Enthalpy: Enthalpy is a measure of the total heat energy absorbed or released in a thermodynamic system. It is also measured in joules but can be expressed in joules per mole, making it more versatile than energy.

The relationship between energy and enthalpy can be established through the general law of thermodynamics, which deals with quantities like temperature, heat, work, internal energy, and their relation.

Enthalpy can be calculated using the formula: $$H = E + PV$$, where $$H$$ is enthalpy, $$E$$ is energy, $$P$$ is pressure, and $$V$$ is volume. However, in most cases, the change in volume ($$PV$$) is negligible, and enthalpy is approximately equal to energy.

In summary, while energy represents the total energy in a system, enthalpy represents the total heat energy absorbed or released in a system. Both energy and enthalpy are measured in joules, but enthalpy can also be expressed in joules per mole, making it more versatile for certain applications in thermodynamics.

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  • What is the Difference Between Energy and Enthalpy?
  • Comparative Table: Energy vs Enthalpy

    • Comparative Table: Energy vs Enthalpy

    Here is a table comparing the differences between energy and enthalpy:

    Property Energy Enthalpy
    Definition Energy is the ability to do work or produce heat. Enthalpy is the sum of internal energy and pressure-volume work. It is a measure of the total heat energy content in a thermodynamic system.
    Abbreviation E H
    State Function Energy is a state function, meaning its value depends only on the current state of the system. Enthalpy is also a state function, as its change depends only on the initial and final states, not on the process itself.
    Measurement The absolute value of energy cannot be measured directly. The absolute value of enthalpy cannot be measured directly.
    Change The change in energy (ΔE) can be derived from the work done on a system and the heat added to it. The change in enthalpy (ΔH) is more useful than its absolute value, as it represents the energy transfer between a system and its surroundings during a chemical or physical process.
    Chemical Reactions Energy is transferred during chemical reactions, and chemical reactions are performed by converting one form of energy into another. Enthalpy is used to describe energy transfer during chemical or physical processes. A positive change in enthalpy indicates an endothermic reaction, while a negative change in enthalpy indicates an exothermic reaction.
    Thermodynamic Work When a substance performs thermodynamic work, it borrows energy from the environment or releases energy to the environment, which either adds to or subtracts from the internal energy. Enthalpy is the sum of internal energy and work energy that exists in all substances. It is expressed as H = U + PdV, where H represents enthalpy, U represents internal energy, P represents pressure, and dV represents volume changes if the substance is a gas.

    In summary, energy and enthalpy are both forms of energy, but they have different definitions and applications in thermodynamics. Energy is the ability to do work or produce heat, while enthalpy is a measure of the total heat energy content in a thermodynamic system. Both energy and enthalpy are state functions, meaning their values depend only on the current state of the system.

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    Guilherme Mazui

    Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.