Physicist Johannes Diederik van der Waals was born in 1837.

Winner of the Nobel Prize for Physics in 1910, Johannes Diederik van der Waals added much to our scientific knowledge. Though he was mostly self-educated, van der Waals was offered the opportunity to pursue his research at the University of Leiden, where he wrote his doctoral treatise "On the Continuity of the Liquid and Gaseous State.” His primary work was on the gaseous and liquid states of matter, and it was this work that made possible later studies of temperatures near absolute zero. Van der Waals built on earlier work dealing with gases, but unlike his predecessors, his work took into account the true nature of gases. Van der Waals realized that gases must have at least some volume and attractive forces between molecules, however small they may be. This assumption helped him produce what is known as the “van der Waals equation.” It was for his work in developing this equation that he was awarded the Nobel Prize. Later, the weak attractive forces between atoms, forces he had correctly attributed even to gas molecules, were named the van der Waals forces in his honor.

Science NetLinks
The purpose of the Science NetLinks lesson A Matter of State (6-8) is to help students understand that particle movement changes as a substance changes from one phase to another phase. Students observe water condensing from its gaseous form. Before this lesson, students should have been introduced to the notion that matter may go through different phase changes. They should understand that temperature plays an important role in determining the state in which a particular type of matter is found. Students should be familiar with solids, liquids and gases. They should also understand that heating and cooling a system can affect the phase of that matter.

The primary purpose of the activities in Temperature Changes Everything (6-8) is to introduce the students to the concept that temperature causes molecules and atoms to move faster and farther apart, which in turn causes the change from solid to liquid, and liquid to gas. Students need to come to this activity with the knowledge that some solids turn into liquids when heated. They also need to understand the observable differences between a solid and a liquid.

The water cycle is of great importance to life on earth, and students should develop an understanding of evaporation, condensation and the conservation of matter. In Models of the Water Cycle (6-8), students build and reflect on the usefulness of models that demonstrate the cycling of water in a closed system. In the process, they observe and learn to recognize evidence of condensation and evaporation.

Believe it or not, the attractive forces between gas molecules are strong enough to hold together entire planets made of gas. Scientists have long thought that huge, gaseous planets like Jupiter and Saturn took at least a million years to form. New research, however, shows that it might not have taken that long at all. Students learn why in Gas Giant Origins (6-12).