Heat

In physics, heat, symbolized by Q, is defined as energy in transit. more...

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Generally, heat is a form of energy transfer associated with the different motions of atoms, molecules and other particles that comprise matter when it is hot and when it is cold. High temperature bodies, which often result in high heat transfer, can be created by chemical reactions (such as burning), nuclear reactions (such as fusion taking place inside the Sun), electromagnetic dissipation (as in electric stoves), or mechanical dissipation (such as friction). Heat can be transferred between objects by radiation, conduction and convection. Temperature, defined as the measure of an object to spontaneously give up energy, is used as a measure of the internal energy or enthalpy, that is the level of elementary motion giving rise to heat transfer. Heat can only be transferred between objects, or areas within an object, with different temperatures (as given by the zeroth law of thermodynamics), and then, in the absence of work, only in the direction of the colder body (as per the second law of thermodynamics).

History

The first to have put forward a semblance of a theory on heat was the Greek philosopher Heraclitus who lived around 500 BC in the city of Ephesus in Ionia, Asia Minor. He became famous as the "flux and fire" philosopher for his proverbial utterance: "All things are flowing." Heraclitus argued that the three principle elements in nature were fire, earth, and water. Of these three, however, fire is assigned as the central element controlling and modifying the other two. The universe was postulated to be in a continuous state of flux or permanent condition of change as a result of transformations of fire. Heraclitus summarized his philosophy as: "All things are an exchange for fire."

As early as 460 BC Hippocrates, the father of medicine, postulated that:

The hypothesis that heat is a form of motion was proposed initially in the 12th century. Around 1600, the English philosopher and scientist Francis Bacon surmised that:

This echoed the mid-17th century view of English scientist Robert Hooke, who stated:

In 1761, Scottish chemist Joseph Black discovered that ice absorbs heat without changing temperature when melting. From this he concluded that the heat must have combined with the ice particles and become latent. Between 1759 and 1763 he evolved that theory of "latent heat" on which his scientific fame chiefly rests, and also showed that different substances have different specific heats. James Watt, who later invented the Watt engine, was Black's pupil and assistant.

In this direction, the ability to be able to use heat transfer to generate work allowed the invention and development of the steam engine by people such as Thomas Newcomen and James Watt. In addition, in 1797 a cannon manufacturer Sir Benjamin Thompson, Count Rumford, demonstrated through the use of friction it was possible to convert work to heat. To do this, he designed a specially shaped cannon barrel, thoroughly insulated against heat loss, then replaced the sharp boring tool with a dull drill bit, and immersed the front part of the gun in a tank full of water. Using this setup, to the amazement of his onlookers, he made cold water boil in two-and-half-hours time, without the use of fire.

Read more at Wikipedia.org