Joseph Black (1728-1799) was a Scottish physician and a leading researcher in th
ID: 2016566 • Letter: J
Question
Joseph Black (1728-1799) was a Scottish physician and a leading researcher in the middle of the eighteenth century. He refined and sharpened the concepts of temperature and heat and was probably the first to recognize the significance of the thermal interactions taking place during the processes of melting and freezing. He wrote: "Melting has been universally considered as produced by the addition of a very small quantity of heat to a solid body, once it has been warmed up to its melting pointIt was believed that this small addition of heat during melting was needed to produce a small rise in temperature as indicated by a thermometer." The opinion I formed is as follows. When ice or any other sold substance is melted .. a large quantity of heat enters itwithout making it apparently warmerI affirm that this large addition of heat (without change in temperature] is the principal and most immediate cause of the liquefaction induced" If the common opinion had been well founded- if the complete change of ice and snow into water required only the addition of a very small quantity of heat-the massought to be all melted within a few minutes or seconds by the heat incessantly communicated from the surrounding airthe consequences of it would be dreadful.. This sudden liquefaction does not actually happen. The masses of ice and snow require a long time to melt." Discuss Black's argument by translating it into your own words and connecting it to your own experiences. From a modern perspective what is wrong with Black's choice of words when referring a "quantity of heat entering a solid body". What misimpression does this phraseology give about the nature of heat?Explanation / Answer
a)He is talking about the specific heat of an object. That is certain things like water will not change form for example from ice to water until a specific amount of heat has been transfered to it. b)There is no such thing as heat because it is only the transfer of the movement of the atoms in the things and refered to the energy of the system. Heat is not a thing and cannot be quantitanized like energy can be.
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