Abstract:
There are three distinct states of matter.- solid liquid and gas. The liquid state is intermediate between the solid and the gaseous states and therefore it is to be expected that the thermodynamic properties of a liquid will be intermediate between those of its solid and gaseous states. But because of the peculiar properties of the liquid state and intensive interaction among the particles in strong disorder, the theoretical analysis of the problem becomes difficult and remains much less developed in contrast with the theory of gases and solids. This is not for want of trying. A vast number of researches have been devoted to attempts to analyze the structure of liquids, either directly by the diffraction methods which have proved so successful in crystalline solids, or indirectly, through the construction of models and their thermodynamic testing. But we still lack either an adequate picture of the arrange-ment of molecules in a liquid or the necessary quantitative theory to explain their thermal and other properties.
The attempts that have been made to formulate a
theory of liquids fall into four broad classes
(i Simulation studies
(ii Integral equation methods
(iii Lattice theories
(iv Perturbation theories.
None of the above theories is adequate description of the liquid state structure, and so far by no means the problem of liquid state is completely solved. Though the perturbation theories are in the process of developing into
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a consistent theory but so far only it has been proven that they are physically satisfying approach to the theory of the equilibrium properties only and that is too in case of simple liquids not for non simple liquids like water. That is why'the liquid state research is an emerging field which will keep physicists attention occupied in the coming decades.
