4.Main Content
Molecules in motion
Introduction
Called 'kinetic theory', this is one of the 'big ideas' in science. All matter is made of atoms (often molecules), but with an enormous variety of arrangements and different motions.
These experiments lead students from the classification of solids, liquids and gases into considering why there is this variety of forms. They might build theories about the atomic structure of matter, guided by the hints given by many experiments. The models could then be tested by further experiments.
The idea that gas pressure is due to bombardment by tiny moving particles, the molecules of a gas, represents one of the great triumphs of Newtonian thinking. In the nineteenth century, this idea proved fruitful in its match with the macroscopic behaviour of gases. In the twentieth century, an appreciation of its shortcomings led to new insights.
Experiment collections
- Evidence for atoms
- From crystals to atoms
- Changes of phase
- Thermal expansion
- Physical models for kinetic theory
- Brownian motion and diffusion
- Boyle's law
- Gas laws and absolute zero
- Molecular speeds
- Finding the size of atoms
- Pressure and density of air
- Mean free path
Guidance
- Crystals and atomic models for beginners
- The separation of molecules in a gas
- Kinetic theory models
- Equi-partition of energy
- A simple theory of a gas
- Brownian motion: facts and myths
- Making dry ice
- Estimating the size of a molecule using oil
- From the pressure law to the Kelvin scale
- Theoretical thoughts: extrapolation
- Avogadro's number and the mass of an air molecule
- Estimate of molecular size: a more formal method
Updated 10 Mar 2010
End of Section Back to top