van der Waals, Johannes Diderik (yōhäˈnəs dēˈdərĭk vän dər väls) [key], 1837–1923, Dutch physicist. It had been known for some time that the behavior of real gases differs from that of an ideal gas as predicted by thermodynamics and the kinetic-molecular theory of gases. Van der Waals was led to the hypothesis of the continuity of the gaseous and liquid states of matter by combining the kinetic theory of gases with Laplace's theory of capillarity. In his theory of corresponding states (1880) he presented an equation of state (now named for him) for homogeneous substances in terms of pressure, volume, and temperature (see gas laws); unlike the ideal gas law, his equation contains constant factors (different for each real substance) to account for the fact that molecules are of finite size and experience weak forces of mutual attraction (now called van der Waals forces). For that work and for discovering the law of binary mixtures he received the 1910 Nobel Prize in Physics. He was professor (1877–1907) at the Univ. of Amsterdam.
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