PROPERTIES of MATTER ANALOGIES

According to Graham's Law, the velocity or rate of diffusion of a gas is inversely related to the square root of the molecular mass. Thus, molecules of small mass travel more rapidly and molecules of larger mass travel more slowly. This idea can be easily remembered by considering the following analogy:

Consider 10 runners who were so closely matched that they had essentially equal times for running a 1000 metre race. Now suppose half of the runners were required to carry an extra 10 kg mass that was attached to them by a belt or backpack. Likely the 5 who had to carry the extra mass would now lag behind the rest of the runners.

Source: Based on Toon, E.R. and Ellis, G.L. Foundations of Chemistry New York: Holt, Rinehart and Winston, 1973 p. 136

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The mean free path is the average distance which a molecule travels between collisions with neighboring molecules. This is like riding in the bumper cars at a carnival ... you only can travel a short distance, on the average, before being involved in a collision with another bumper car.

Source: Original

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Students in a classroom are analogous to the particles of a solid, since they have a regular arrangement and a limited freedom of movement. Students shifting or turning in their seats represent the vibrational motion of solid particles.

During breaks between classes, students have a wider range of motion. They now also have limited translational motion which allows them to move among one another to the doorway and through the halls, but are still confined to the volume of the school. This is analogous to the behaviour of liquid particles.

At the end of the day, students are like gas particles since they have unrestricted and primarily translational motion which causes them to escape from their school building and diffuse throughout the community.

Source: Licata, Kenneth P. Chemistry Is Like A ... The Science Teacher 1988, 55(8), 42.

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