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Waals, Johannes Diderik van der

gases gas real physics

[van der vahls ] (1837–1923) Dutch physicist: devised a new equation of state for gases.

Van der Waals, a carpenter’s son, became a primary school teacher and a headmaster in The Hague. He trained for secondary school work in 1866, and then studied physics at Leiden. His doctoral dissertation on the physics of gases appeared in 1873. His interest was directed to the observations of and others, who had shown that real gases deviate from the simple gas law pV = RT , deduced from kinetic theory for an ‘ideal’ gas whose particles have no volume and no attraction for one another. Real gases follow the law only approximately, and not at all at high pressures or low temperatures. Andrews also showed that a critical temperature exists below which a real gas can be condensed to liquid only by pressure. Van der Waals devised a modified gas equation by introducing two new constants; a is related to intermolecular attraction and b to the volume of the molecules themselves. The new equation of state has the form ( p + a/V 2 )( Vb )= RT , (again for one mole of gas) and with suitable values of a and b gives results in fairly good accord with observation for real gases over a range of temperatures above the critical point. Van der Waals was professor of physics at Amsterdam from 1877 and was awarded the Nobel Prize for physics in 1910.

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