Important Concepts of Heat and Thermodynamics Chapter

The science of the connection between heat, work, temperature, and energy is known as thermodynamics. Thermodynamics, in its broadest sense, is concerned with the movement of energy from one location to another and from one form to another. Heat is a type of energy that corresponds to a specific quantity of mechanical effort, which is the central notion.


Heat wasn’t really officially recognised as a form of energy till about 1798, once Count Rumford, a British military engineer, discovered that infinite amounts of heat could be produced while boring cannon barrels, and also that the heat generated is proportional to the amount of work done in turning a blunt boring tool. The cornerstone of thermodynamics is Rumford’s observation of the relation between heat created and work done. Sadi Carnot, a French military engineer, was another pioneer, introducing the heat-engine cycle and the theory of redox potential in 1824. Carnot’s research focused on the limits to the greatest amount of work that a steam engine can do while using a high-temperature heat transfer just like its driving force. Rudolf Clausius, a German mathematician & scientist, expanded these concepts into the first and second principles of thermodynamics, respectively, subsequently that century.

Laws Of Thermodynamics

The following are the most significant thermodynamic laws:

  • Fundamental law of thermodynamics zero. The first two systems are in thermal equilibrium with each other when they are each in thermal equilibrium with a third system. This trait enables using thermometers as a “third system” and defining a temperature scale meaningful.
  • The first law of thermodynamics, sometimes known as the law of energy conservation. The difference between heat given to the system from its surroundings and work done by the system on its surroundings equals the change in a system’s internal energy.
  • The second law describes how heat is transferred from one place to another. Heat does not naturally flow from a colder to a hotter location, or, to put it another way, heat at a particular temperature cannot be turned totally into work. As a result, the entropy of a closed system, or the amount of heat energy per unit of temperature, grows with time, eventually reaching a maximum value. As a result, all closed systems converge to a state of equilibrium where entropy is greatest and no energy is available to conduct beneficial work.
  • The Third Law of Thermodynamics is one of the most important laws of thermodynamics. As the temperature approaches absolute zero, the entropy of a perfect crystal of an element in its most stable state tends to zero. This enables the creation of an absolute entropy scale that, from a statistical standpoint, defines the degree of randomness or disorder in a system.

Although thermodynamics grew fast in the nineteenth century in response to the need to improve the performance of steam engines, the rules of thermodynamics’ vast universality make them relevant to all physical and biological systems. The rules of thermodynamics, in particular, provide a comprehensive explanation of all changes in a system’s energy state and its capacity to do beneficial work on its surroundings. This post is about classical thermodynamics, that does not take individual atoms and molecules into account. Statistical thermodynamics, often known as statistical mechanics, is a branch of thermodynamics that describes macroscopic thermodynamic features in terms of the behaviour of individual particles and their interactions. Its origins may be traced back to the late 1800s, when atomic and molecular theories of matter were widely recognised.

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Thermodynamic States

The implementation of thermodynamic principles starts with the definition of a system that is unique from its surroundings in some way. A sample of gas within a cylinder with a moveable piston, a whole steam engine, a marathon runner, the planet Earth, a neutron star, a black hole, or even the entire universe, for example, might constitute the system. Systems can freely exchange heat, work, and other kinds of energy with their environment in general. The thermodynamic state of a system refers to its current state. The temperature, pressure, and volume of a gas in a cylinder with a moveable piston determine the state of the system. These attributes are defining parameters that have defined values at each state and are unaffected by how the system got at that state. In other words, any change in the value of a property is determined only by the system’s initial and final states, not by the path taken by the system from one state to the next. State functions are a type of property that has these characteristics.

Any work done as when the piston advances as well as the gas expands, as well as the heat the gas absorbs from its surroundings, are, on the other hand, dependent on the precise manner in which the gas expands. The behaviour of a complicated thermodynamic system, including such Earth’s atmosphere, may be explained by applying state and property concepts to its constituent parts—in this example, water, water vapour, and the many gases that make up the atmosphere. Properties and their interrelations can be investigated as the system changes from state to state by isolating samples of material whose states and properties can be controlled and modified.

Related question from the chapter: The ratio of the speed of sound in nitrogen gas to that in helium gas, at 300K is?

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