Jethalal S. Zaveri
Prof. Muni Mahendra Kumar
Physical properties like extension (volume), mass, density, etc., can be changed by change in temperature and/or pressure. For instance water is solid (in the form of ice) at temperature 0°C or below. When heated, it becomes liquid and its volume slightly increases. At 100°C, it boils and changes into steam, which has very much larger volume. Similarly air (or oxygen) which is gaseous at normal temperature and pressure can be liquefied under very high pressures. The thermal motion in a solid body is quivering or [1] vibration of molecules. If the body is heated, the quivering becomes stronger and at the melting point the molecules leave their places and begin to move. At still higher temperatures, they fly apart in all directions and the result is gaseous state of matter.[2] But the change is in the physical properties only. Ice, water and steam are all chemically the same compound H2O and molecules retain their molecular identities. The modification of physical properties and the consequent transformation of one kind of energy into another is perhaps a typical instance of parinama.
[1] Temperature of liquid air is 63° absolute or 210° C below zero.
[2] If the temperature is raised still farther, thermal dissociation takes place and the molecules are broken up into separate atoms. For instance, molecules of water will be broken up at a temperature over a thousand degrees. But when the temperature rises to several thousand degrees, the matter will be a gaseous mixture of pure elements. At still higher temperatures, thermal ionisation takes place when outer electrons are chipped off from the atoms At a few million degrees (temperature common in the interiors of stars) all electronic shells are completely stripped off and matter becomes a mixture of bare nuclei and free electrons If the temperature goes up to several billion degrees the nuclei themselves break up into protons and neutrons. Thus the effect of thermal agitation is to destroy step by step the elaborate architecture of matter into particles rushing around without any apparent law.
[2] Parispandana-laksana kriya - Pravacanasara Pradipika Vrtti, 2-37.
