Changes of state

1873 Changes of state

The book of science

Tom Sharp

Johannes Diederik van der Waals chemistry Changes of state

Changes of state

Atoms in a gas are not infinitely small or unaffected by one another. They are not merely kinetic Newtonian objects with probable velocities moving at random far apart in space. If they were, the pressure of a gas would vary smoothly with its temperature. Johannes Diederik van der Waals modified the kinetic theory of gases developed by Maxwell and Boltzmann to account for a molecule’s size and its affects on its neighbors. His equation let him predict the phase transitions between stable states where a gas becomes a liquid or a liquid becomes a gas.

Van der Waals forces

Tiny hairs on the toes of a gecko stick to leaves, ceilings, even plate glass because they get extremely close where small temporary or permanent polarizations cause molecules to act like magnets.

Making things happen

Science cannot predict when a look becomes a laugh. Two magnets may repel or attract. Although a state of mind may be valuable, it would be more profitable if it were more predictable.

Newton taught that on the universal scale mathematics brings light to physics; Van der Waals applied mathematics on the atomic scale to explain the behavior of gases and the changes of state from solid, to liquid, to gas. Results of physical experiments demanding explanations suggest that an interplay between mathematics and physics is essential.

Van der Waals was influenced by the thermodynamics of Rudolf Clausius and the writings of James Clerk Maxwell, who praised his work.

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