Difference Between Adiabatic and Isothermal (With Table)

The isothermal and adiabatic processes are used in thermodynamics to explain the behavior of a thermodynamic process and its relationship to temperature variations. The distinction between isothermal and adiabatic reactions must be grasped to comprehend its actual industrial use. Both of these processes are mentioned more in thermodynamics. Both of these processes are opposed.

Adiabatic vs Isothermal

The major distinction between adiabatic and isothermal processes is that adiabatic processes take place at different temperatures, whereas isothermal processes take place at a constant temperature. The most significant difference between the two parts of the process is that the adiabatic process does not include heat transport to or from the liquid. On the other hand, heat is transferred to the environment to maintain a constant temperature in the isothermal process.

Difference Between Adiabatic and Isothermal

The adiabatic process happens when there is no heat transfer between such a system and its environment. To avoid unwanted heat transmission, the system’s temperature should be adjusted. This adiabatic process may be reversible or irreversible.

An isothermal process occurs at a fixed temperature, but other system parameters can be altered. It is a thermodynamics phenomenon in which the temperatures of a system do not change over time. Heat is transferred into and out of the system relatively slowly to maintain thermal equilibrium. The isothermal Process is changing a material, item, or even a system at a constant temperature.

Comparison Table Between Adiabatic and Isothermal Process

PressureAt a given volume, the pressure is lower.At a given volume, the pressure is higher.
Heat TransferHeat transfer doesn’t take place.Heat transfer takes place.
TemperatureThe internal system variations cause temperature changes.The temperature remains constant.
EnthalpyEnthalpy changes within the process.Enthalpy remains constant.
ExampleGas expanding in a vacuum container.Formation of ice from water.

What is Adiabatic?

An adiabatic process is a thermodynamic process that occurs when there is no heat transfer between a system and its surroundings. In this case, neither heat nor energy is transported into or out of the system. As a result, effort is the only method for energy to be transferred between a body and its environment in an adiabatic process. It might be either irreversible or reversible.

The settings of a piston, such as with a piston in a gasoline engine, are an instance when adiabatic processes are relevant. The gas shall contract as the piston’s pressure rises. Decompression causes the gas to expand again, causing the piston to move. Adiabatic mechanisms are in charge of this.

Adiabatic expansion is the idealized behavior of a system in which the temperature continues to rise, but the pressure remains constant. It refers to a sealed system in general.

The higher internal energy of the airflow in the system equals the exterior work done. In this case, the heat from the surrounding atmosphere is not eliminated or added to the system air. The operating pressure tends to exceed the volume as the temperature rises.

By doing the operation fast, an adiabatic process may be maintained. For instance, if we compress a gas fast in cylinders, the system will not have enough time to transmit thermal energy to the surroundings. The system’s work modifies the system’s inner energy in adiabatic processes.

What is Isothermal?

An isothermal process is one in which the temperature stays constant despite changes in pressure and volume. Boyle’s gas law in thermodynamics connects pressure, temperature, and volume. If one remains unchanged, the others will alter in proportion to it. Whenever the pressure and volume of the gas are inversely proportional, the temperature of a gas remains constant.

Heat must be moved into or relocated out of the system to maintain the system’s temperature constant.

For example, when a material, like water, reaches its melting or boiling point, the pressure and temperature stay constant despite phase, volume, and heat energy changes.

The Carnot engine is an important manufacturing utilization of the isothermal process. To keep the system’s temperature stable, work should be done here on systems or by the systems in the environment; working on the gases increases energy, which raises the temperature.

However, if the temperature increases over the setpoint, the system begins to function in the environment. However, When the system’s temperature drops, the energy is released as heat into the environment.

Main Difference Between Adiabatic and Isothermal

  • In an adiabatic system, the temperatures of a gas decrease as it expands, whereas in an isothermal system, the temperature remains constant as the gas expands.
  • In an adiabatic system, pressure is inversely proportional to volume, whereas pressure in an isothermal system is inversely proportional.
  • In an adiabatic system, heat does not vary, but it does in an isothermal system.
  • In an adiabatic process, internal energy changes, causing expansion, but in an isothermal process, expansion occurs by absorption of heat from the environment.
  • An adiabatic process system is thermally separated from its surroundings. It requires an isolated system, whereas an isothermal process system is not thermally insulated from its surroundings and thus requires an open or closed system.
  • The work done in an adiabatic process is due to changes in internal energy, whereas the work done in an isothermal process is due to the system’s net heat content.
  • An adiabatic system compresses by adding heat to the system’s internal energy, while an isothermal system compresses by losing heat to the environment.


The adiabatic process requires two important conditions:

  • The system should be isolated from its surroundings; and
  • The process must happen swiftly enough to allow enough time to transfer heat.

In general, the isothermal process can function under two conditions: 

  • This occurs when the surrounding temperature (T) is less than the temperature of the system (TS), i.e., T < TS, and no thermal equilibrium is maintained. 
  • This occurs when the external temperature is higher than even the temperatures of the system and thermal equilibrium is not maintained.

The adiabatic and isothermal processes involve pressure, temperature, and volume. They’re all quite drawn with gases as well. In planetary atmospheres, both sorts of processes are crucial.


  1. https://aapt.scitation.org/doi/pdf/10.1119/1.2344391
  2. https://link.springer.com/article/10.1007/s11005-005-4838-1
  3. https://pubs.rsc.org/en/content/articlehtml/2014/rp/c4rp00008k

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