Name: isothermal expansion and heat transfer
Uploaded: 2025-08-19T15:10:28.000Z
Duration: 1 min 21 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Energy

HS-PS3-4

Isothermal Processes

Un proceso termodinámico que ocurre a una temperatura constante se denomina proceso isotérmico.
La conversión de agua hirviendo en vapor a una temperatura constante de 100 grados centígrados es un ejemplo de proceso isotérmico. Del mismo modo, la conversión de agua en hielo a 0 grados centígrados también es un proceso isotérmico.
El cambio en la energía interna es cero para estos procesos, ya que la temperatura no cambia. Así, utilizando la primera ley de la termodinámica, el trabajo realizado es igual al calor.
Ahora, considere un sistema de gas ideal encerrado en una jeringa de gas sellada a una temperatura constante.
Cuando el émbolo se empuja lentamente de manera controlada, el gas dentro de la jeringa se comprime. La reducción del volumen del gas provoca un aumento de la presión, sin embargo, la temperatura se mantiene constante.
La liberación del émbolo de forma controlada conduce a una expansión del gas a temperatura constante.
La curva pV para cualquier proceso isotérmico es hiperbólica, ya que la presión es inversamente proporcional al volumen para un gas ideal a una temperatura constante.

<ol>
	<li>Young, H. D, y Freedman, R.A. (2012). Física Universitaria con Física Moderna. San Francisco, CA: Pearson. págs. 635.</li>
	<li>OpenStax. (2019). Física Universitaria Vol. 2. [Versión web]. pp 121 Obtenido de <a href="https://openstax.org/books/college-physics/pages/15-2-the-first-law-of-thermodynamics-and-some-simple-processes">https://openstax.org/books/college-physics/pages/15-2-the-first-law-of-thermodynamics-and-some-simple-processes</a></li>
</ol>

procesos isotérmicos

Un proceso termodinámico que ocurre a temperatura constante se llama proceso isotérmico. El calor fluye lentamente hacia el sistema o fuera del sistema para mantener el equilibrio térmico. Los procesos que involucran cambios de fase, como la evaporación del agua en vapor o la congelación del agua en hielo a una temperatura constante, son ejemplos de procesos isotérmicos. Un gas ideal también puede experimentar una expansión o compresión isotérmica. Por ejemplo, considere 1 mol de un gas ideal dentro de un cilindro aislado con un volumen inicial V y una presión p. Supongamos que el calor agregado al sistema causa una expansión cuasiestática del gas a una temperatura constante de 300 K. Si el volumen del gas cambia a 2V, ¿cuál es la magnitud de calor agregado al sistema? Aquí, las magnitudes conocidas son el número de moles del gas, el volumen inicial y final del gas. La magnitud desconocida, el calor, debe ser calculada. De acuerdo con la primera ley de la termodinámica, <img alt="Equation1" src="/files/ftp_upload/13682/13682_Equation_PT_1.svg" style="text-align: center; height: 13px;"> Como la temperatura es constante, el cambio en la energía interna para este proceso es cero. Por lo tanto, el calor agregado al sistema es igual al trabajo realizado por el sistema. <img alt="Equation2" src="/files/ftp_upload/13682/13682_Equation_PT_2.svg" style="text-align: center; height: 13px;"> Ahora, el trabajo realizado por un gas ideal durante una expansión isotérmica se da por, <img alt="Equation3" src="/files/ftp_upload/13682/13682_Equation_PT_3.svg" style="text-align: center; height: 32px;"> Sustituyendo el número de moles, la constante del gas, la temperatura, el volumen inicial y el volumen final del gas, el trabajo realizado es igual a 1728.85 J. Dado que el trabajo realizado por el sistema es igual al calor agregado al sistema, se considera que se aplicaron 1728.85 J de calor al sistema para expandirlo isotérmicamente a 2V.

Procesos isotérmicos

Un proceso termodinámico que ocurre a temperatura constante se denomina proceso isotérmico. El calor fluye lentamente hacia el sistema o fuera del sistema ...

Education

Educación

JoVE Core

Physics

Física

Unit 1

Unidad 1

The First Law of Thermodynamics

La primera ley de la termodinámica

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

isothermal expansion and heat transfer

An isothermal process is a thermodynamic process that happens at constant temperature. During the process, heat slowly flows into the system or out of the system so thermal equilibrium is maintained.

Phase changes are common examples of isothermal processes. Water can evaporate into steam at a constant temperature, and water can also freeze into ice at a constant temperature. An ideal gas can also undergo isothermal expansion or compression.

Here, an ideal gas in an isolated cylinder expands quasistatically at 300 K. The gas starts with 1 mole at volume V and pressure p. The volume then changes to 2V, and the heat added to the system must be found.

By the first law of thermodynamics, the change in internal energy is zero because the temperature stays constant. That means the heat added to the system equals the work done by the system. For an ideal gas in isothermal expansion, the work is calculated from the initial and final volume.

Substituting the number of moles, gas constant, temperature, and volumes gives a work value of 1728.85 J. Since the work done by the gas equals the heat added, 1728.85 J of heat is applied to expand the gas isothermally to 2V.

Isothermal Expansion and Heat Transfer

thermodynamic systems

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A thermodynamic system is the part of the world that scientists study for its heat and energy behavior. It sits inside a surrounding environment, or surroundings. The system and the surroundings can exchange heat and do work across the boundary that separates them. The immediate surroundings affect the system most strongly because they interact with it directly. A kettle of boiling tea shows how this works in everyday life. The tea and the kettle together form the system. If the lid is open,...

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path between thermodynamics states

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isothermal processes

An isothermal process is a thermodynamic process that happens at constant temperature. During the process, heat slowly flows into the system or out of the system so thermal equilibrium is maintained. Phase changes are common examples of isothermal processes. Water can evaporate into steam at a constant temperature, and water can also freeze into ice at a constant temperature. An ideal gas can also undergo isothermal expansion or compression. Here, an ideal gas in an isolated cylinder expands...

isochoric and isobaric processes

Constant Volume and Pressure in Thermodynamics

Thermodynamic processes can happen at constant volume or at constant pressure. An isochoric process is a constant-volume process. In this case, the volume does not change, so the work done by the system is zero. The first law of thermodynamics still applies, so any heat added or removed changes the internal energy of the system only. A simple example is heating 1000 g of water from 40 degrees celsius to 70 degrees celsius at constant volume. Because the process is isochoric, no work is done by...

heat capacities of an ideal gas i

Ideal Gas Heat Capacity at Constant Pressure

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heat capacities of an ideal gas ii

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adiabatic processes for an ideal gas

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pressure and volume in an adiabatic process

pressure-and-volume-in-an-adiabatic-process

Free Expansion: Pressure, Volume, and Temperature

Free expansion shows how pressure, volume, and temperature behave when a gas expands without doing work. It is an adiabatic process, but it is not the same as adiabatic expansion. In free expansion, no work is done and the internal energy does not change. In adiabatic expansion, work is done and the internal energy changes. For an adiabatic process, the pressure-volume relation comes from the adiabatic condition. That relation does not apply to free expansion, even though the expansion is...

work done in an adiabatic process

Adiabatic Compression in an Engine Cylinder

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thermodynamic potentials

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maxwell's thermodynamic relations

Using Maxwell's Relations in Thermodynamics

Maxwell's thermodynamic relations help solve problems in thermodynamics. They connect partial differentials for quantities that are hard to measure in the lab with quantities that are easier to measure. This makes them useful for working with temperature, pressure, volume, and entropy. These relations come from thermodynamic potentials and the symmetry of second derivatives. Thermodynamic potentials are exact differentials, so the order of second differentiation does not change the result.

joule-thomson effect

Gas Cooling and Heating in Throttling

Gas cooling and heating in throttling is explained by the Joule-Thomson effect, also called the Joule-Kelvin effect. It describes how a fluid changes temperature when it passes through a valve or porous plug in a thermally insulated system. This type of flow is called a throttling process. In the experiment, a high-pressure gas is forced through a throttle valve or porous plug into a lower-pressure region. The gas expands as it moves into the larger volume. Work is done on the gas as it is...

key terms and concepts

Learn how isothermal processes keep temperature constant while heat equals work during ideal gas expansion, with phase change and cylinder examples.

Isothermal Expansion and Heat Transfer | JoVE K12

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JoVE Core Física presenta la teoría y la aplicación de conceptos físicos fundamentales, como la cinemática, dinámica, mecánica de fluidos, estática, ondas y acústica, mediante animaciones audiovisuales concisas y fáciles de entender. Además, los vídeos de científicos en acción muestran la aplicación de los conceptos relacionados en experimentos de investigación clásicos y originales, realizados en laboratorios de todo el mundo.

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Physical Science

HS-PS3-1

Florida Department of Education

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SC.912.P.10.2

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HS-PS3-3.

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HS-PS3-6

Isothermal Expansion and Heat Transfer

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