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The science of physics studies objects and systems to measure their motions, temperatures, and other characteristics. Physical concepts can be applied to anything from single-celled organisms to mechanical and subatomic systems, planets, stars, galaxies, and all the processes that govern them. Within physics there is thermodynamics, which is a branch that focuses on energy changes (heat) and on the properties of a system during any physical or chemical reaction.
An isothermal process is a thermodynamic process in which the temperature of a system remains constant . Heat transfer into or out of the system occurs so slowly that thermal equilibrium is maintained. The word thermal is a term that describes the heat of a system, “iso” means “equal”, so “isothermal” means “equal heat”, which is what defines thermal equilibrium.
The isothermal process
In general, during an isothermal process there is a change in internal energy, thermal energy, and work; Although the temperature always remains constant, something in the system works to keep that temperature the same, an ideal example being the Carnot cycle, which basically describes how a heat engine works by supplying heat to a gas. As a result, the gas expands in a cylinder and pushes a piston to do the work; then the heat or gas must be expelled from the cylinder (or discharged) in order to make room for the next heat/expansion cycle. This reference that is mentioned is a clear example of what happens inside the engine of a vehicle with a combustion engine.
If the explained cycle is completely efficient, the process is isothermal, because the temperature remains constant while the pressure changes.
To understand the basic concepts of the isothermal process, we must take into account the action of gases in a system. The internal energy of an “ideal gas” depends only on temperature, so the internal energy change during an isothermal process for an ideal gas is equal to 0; all heat added to a system does work to keep the process isothermal, as long as the pressure remains constant. When considering an ideal gas, the work done on the system to maintain the temperature suggests that the volume of the gas must decrease as the pressure in the system increases. According to the ideal gas law, pressure varies linearly with temperature and quantity, and inversely with volume.
Isothermal processes and states of matter
Isothermal processes are many and varied. The evaporation of water into the air is one of them, as is the boiling of water to a specific boiling point.
There are also many chemical reactions that maintain thermal equilibrium, and in biology the interactions of a cell with its surrounding cells (or other materials) are said to result in an isothermal process.
Evaporation, melting, and boiling are also phase changes, that is, they are changes in water or other fluids or gases that take place at constant temperature and pressure.
Tracing an isothermal process
In physics, the graphical representation of these reactions and processes is done by means of diagrams (graphs). On a phase diagram, an isothermal process is plotted along a vertical line, or a plane on a 3D diagram, through a constant temperature; the pressure and volume can change to maintain the temperature of the system.
As they change, it is possible for a substance to change its state of matter, even when its temperature remains constant; therefore, the evaporation of water as it boils means that the temperature remains the same as the system of pressure and volume change; this is plotted with temperature (which remains constant) along the diagram.
Applications of the study of isothermal processes
When scientists study isothermal processes in systems, they are really looking at heat, energy, and the connection between them, as well as the mechanical energy needed to change or maintain the temperature of a system. This understanding helps biologists to study how living things regulate their temperature. It also applies to engineering, space science, planetary science, geology, and many other branches of science. Thermodynamic power cycles, and therefore isothermal processes, are the basic idea behind heat engines. These devices are used to power electric power generating plants and, as mentioned above, cars, trucks, planes, and other vehicles; Furthermore, these systems also exist in rockets and spacecraft.
References
https://solar-energia.net/termodinamica/procesos-termodinamicos/proceso-isotermico
https://www.thermal-engineering.org/en/what-is-the-isothermal-process-definition/
University Physics , Sears and Zemansk, Addison-Wesley 2019
