A Brief Guide on Thermodynamic Approach Towards Temperature

Thermodynamics is a scientific discipline that explores how heat and other kinds of energy interact with each other. It discusses how thermal energy is converted into and out of other forms of energy, as well as how it interacts with matter.

Thermodynamics solely deals with a system’s large-scale response, which can be observed and measured in experiments. However, to describe small-scale interactions, we use the kinetic theory of gases. Thermodynamics and heat are governed by three primary laws. Each law aids in the understanding and prediction of a physical system’s operation. 

 Understanding Temperature in Thermodynamics

The temperature, in simple words, is the average kinetic energy of an object’s atoms and molecules that can be used to determine its temperature. Kelvin is the SI unit for temperature in thermodynamics.

 The term temperature describes the energy condition of matter. It is the average kinetic energy of the system’s atoms or molecules. All materials have atoms and molecules that move constantly, and the more they move, the higher the temperature of the substance.

Relationship Between Heat And Temperature

The terms ‘heat’ and ‘temperature’ are two widely distinct but related notions in the context of Thermodynamics.

 The kinetic energy produced by the atoms and molecules in a system is measured by temperature. Each object’s molecules are constantly in motion and clashing with one another at the atomic level. A substantial amount of kinetic energy is exchanged whenever they collide with each other. When the two systems collide, heat is transferred from the hotter to the colder object until the two objects are at the same temperature. When the two systems in contact are at the same temperature, it is known as thermal equilibrium.

On the other hand, heat is the transfer of thermal energy from a hotter to a colder system that is in contact. It is sometimes also referred to as a process quantity because it is defined in the context of an energy transfer process. As heat is a broad property, the temperature change caused by heat transmission to a system is proportional to the number of molecules in the system.

How is Heat Defined in Thermodynamics?

Thermodynamics and heat transfer is concerned with energy systems, including energy conservation and conversion of energy forms, as well as the transmission of thermal energy and component mass via heat transfer and mass transfer, respectively.

Heat has a very definite meaning in thermodynamics that differs from how we could use the word in ordinary conversation. Heat is defined as the movement of thermal energy between two substances that are at different temperatures and come into contact. It is measured in Joules and is represented with the symbol Q or q.

How is Temperature Defined in Thermodynamics?

The following section explains the concept of temperature and how does temperature affect thermodynamics in detail:

Thermodynamic temperature is the absolute measurement of temperature. The second rule of thermodynamics and the presence of reversible heat processes, such as isothermal compression of an ideal gas, give rise to the concept of thermodynamic temperature, and the third law describes it as the lowest temperature at the null or zero point. 

At absolute zero, the matter is in its ground state, which is its lowest energy state and the particle constituents of matter have negligible motion. For two reasons, the thermodynamic temperature is often known as absolute temperature. One, as proposed by Kelvin, that it is independent of the qualities of the material in question, and second, according to the properties of the ideal gas, it refers to an absolute zero.

The Kelvin scale is used as the SI unit of thermodynamic temperature, with the triple point of water at 273.16K serving as the basic fixing point.

Measurement of Thermodynamic Temperature

Based on the Triple Point of water, the International System of Units (SI) provides a scale and a unit for thermodynamic temperature. Instruments known as thermometers are used to measure temperature using these predefined reference points for comparison.

Temperature is usually measured using one of three scales: Celsius, Fahrenheit, and Kelvin. Celsius represents temperature based on two fixed points. While on a Celsius scale, the freezing point is 0 and its boiling point is 100, according to a Fahrenheit scale, the freezing point of water is 32 and it reaches its boiling point at 212.

As already discussed, the SI unit of thermodynamic temperature in Kelvin is represented by the sign K. It was proposed in the year 1848 by William Thomson (Lord Kelvin), a British scientist and mathematician, for the first time. On a Kelvin scale, while the freezing point of water is 273.15 degrees Kelvin, its boiling point is 373.15 Kelvin.

This temperature scale is mostly used in the domain of science and technology only, not in everyday life. Scientists also use the Rankine scale to measure the temperature for various scientific purposes.

Conclusion

Thermodynamics and heat are interrelated. In the discipline of thermodynamics, heat and temperature are the main components and their effect on each other is the key area of study. In thermodynamics, heat transfer and mass transfer are still significant concerns in the creation of the present and future engineering systems and will continue to be critical in meeting the challenges of moving to a sustainable energy future based on solar and biomass, as well as efficient conventional energy sources.