# Thermodynamic Laws and processes explained with the help of GIFs

Thermodynamics' refers to a macroscopic description of bodies and processes. Thermodynamics arose from the study of two distinct kinds of transfer of energy, as heat and as work, and the relation of those to the system's macroscopic variables of volume, pressure and temperature.  Transfers of matter are also studied in thermodynamics. The article features the animations related to laws of thermodynamics and processes associated with it.

## Laws of Thermodynamics

### Zeroth Law of Thermodynamics

Image Courtesy: weelookang.blogspot.com

The zeroth law states that if two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other. As you can see in the animation, that if A and B are in thermal equilibrium with C, then A and B will be in thermal equilibrium with each other if they are brought into contact. Notice thermal equilibrium occurs when there is no net heat flow and TA = 13.4oC = TB = TC.

### First Law of Thermodynamics

Image Courtesy: thermalfluidscentral.org

Image Courtesy: compchem.org

The first law states that the change in the internal energy of a system is equal to the sum of the heat gained or lost by the system and the work done by or on the system. It can also be stated this: The change in the internal energy of a closed thermodynamic system is equal to the sum of the amount of heat energy supplied to or removed from the system and the work done on or by the system. The animation shows a typical thermodynamic system, showing input from a heat source on the left and output to a heat sink on the right. Work is extracted, in this case by a series of pistons. The second animation shows an energy conservation analysis for a simple system.

### Second Law of Thermodynamics

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According to second law of thermodynamics, heat cannot spontaneously flow from a colder location to a hotter location. The second law is an observation of the fact that over time, differences in temperature, pressure, and chemical potential tend to even out in a physical system that is isolated from the outside world. The animation shows an Alpha Type Stirling Engine treated as a Second Law of Thermodynamic Heat-engine, in a closed system. It is a sort of 'External Combustion Engine' as it allows a variety of heat sources and fuels, but it still needs a vent, tailpipe or a chimney. Another way to phrase this law is: Heat cannot spontaneously flow from a colder location to a hotter area - work is required to achieve this.

### Third Law of Thermodynamics

Image Courtesy: physicsforme.com

It states that as a system approaches absolute zero the entropy of the system approaches a minimum value. The animation shows a Szilard engine which is further explained in the picture beneath it. The role of the third law of thermodynamics in the Szilard engine has been addressed. If the ground state is non-degenerate, the entropy production defined as the work extractable from the engine divided by temperature vanishes as temperature approaches zero due to the third law. The degenerate ground state induced by the symmetry or by accidence gives rise to non-zero entropy production at zero temperature associated with the residual entropy.

## Thermodynamic processes

A thermodynamic process may be defined as the energetic evolution of a thermodynamic system proceeding from an initial state to a final state. Typically, each thermodynamic process is distinguished from other processes, in energetic character, according to what parameters, as temperature, pressure, or volume, etc., are held fixed.

### Isobaric Process

Image Courtesy: teachersites.schoolworld.com

It is a process which occurs at constant pressure. The animation is that of a process whereby the pressure remains constant while temperature and volume vary in a system.

### Isochoric process

Image Courtesy: heatenginescience.blogspot.com

An isochoric process is that process which occurs at constant volume. The animation shows a cycle using two constant pressure processes and two constant volume processes. Its representation in a P-V diagram is a rectangle. The rectangle horizontal sides are the isobars and the rectangle vertical sides are the isochoric.

### Isothermal process

Image Courtesy: learneasy.info

Occurs at a constant temperature, this typically occurs when a system is in contact with an outside thermal reservoir, and the change occurs slowly enough to allow the system to continually adjust to the temperature of the reservoir through heat exchange.

Image Courtesy: physics-animations.com

An adiabatic process is one in which no heat is gained or lost by the system. An adiabatic process may be accomplished by thermal insulation or by making rapid changes in volume so that there is no time for heat to be exchanged as shown in the animation.

### Isentropic process

Image Courtesy: popsolving.com

It is a reversible adiabatic process which occurs at constant entropy. The animation shows a complete Carnot cycle in which isentropic process occurs.

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