Johannes Diderik van der Waals (1837 - 1923) was a Dutch theoretical physicist who established the modern understanding of the continuity between the gaseous and liquid states of matter. His derivation of an equation of state accounting for the finite size of molecules and the attractive forces between them earned him the 1910 Nobel Prize in Physics [2] and gave his name to both a fundamental equation and a class of intermolecular forces.
Early life and education
Van der Waals was born on 23 November 1837 in Leiden, in the Netherlands. He began his working life as a schoolteacher and largely educated himself in physics and mathematics before gaining admission to Leiden University, where he pursued advanced study while continuing to teach. [1] Because his early training lacked the classical languages then required, his path to a university degree was unusually long, but he ultimately completed his doctorate at Leiden in 1873.
Doctoral thesis
His dissertation, On the Continuity of the Gaseous and Liquid States, proposed that gases and liquids are not fundamentally distinct but represent two forms of the same substance that pass continuously into one another. To describe this, van der Waals modified the ideal gas law by introducing two corrections: one for the volume occupied by the molecules themselves and one for the attractive forces acting between them. [1] The Scottish physicist James Clerk Maxwell reviewed the work and praised it highly.
Academic career and the equation of state
In 1877 van der Waals was appointed the first professor of physics at the newly reorganised University of Amsterdam, a post he held until his retirement in 1908. [3] The relationship he had derived, now known as the van der Waals equation of state, was the first to describe both the gaseous and liquid phases with a single expression and to predict the existence of a critical point at which the distinction between them vanishes. In 1880 he formulated the law of corresponding states, showing that different substances behave similarly when their pressure, volume, and temperature are expressed relative to their critical values.
Nobel Prize and later work
The law of corresponding states proved of great practical importance, guiding experimental efforts to liquefy gases; it informed the work of Heike Kamerlingh Onnes, who later achieved the liquefaction of helium at Leiden. In 1910 van der Waals received the Nobel Prize in Physics for his research on the equation of state for gases and liquids. [2] He continued to publish on molecular theory, including work on the behaviour of mixtures and on capillarity.
Legacy
Van der Waals died in Amsterdam on 8 March 1923. His name survives in everyday scientific vocabulary: the weak, short-range attractions between neutral molecules are called van der Waals forces, and his equation remains a standard teaching tool for introducing the behaviour of real, non-ideal gases. [2] His insistence that macroscopic properties could be explained by the interactions of molecules helped establish molecular physics as a rigorous, quantitative discipline.
