Unit 7
Gases
Why does a balloon inflate? What does a thermometer actually measure? Inside a genuinely running molecular-dynamics box you will measure Boyle’s law yourself, watch the Maxwell speed distribution emerge, count molecules through Brownian motion, and find out when real gases stop behaving ideally.
- 1 Gas laws: where pressure comes from Pressure is the drumming of countless molecules on the walls. Change volume, temperature, and particle number in a molecular-dynamics box, plot the measured pressure, and the ideal gas law emerges on its own. 25 min
- 2 Kinetic theory and the speed distribution Temperature measures the average kinetic energy of molecules. Molecules do not all share one speed; their speeds follow the Maxwell–Boltzmann distribution. 25 min
- 3 Mixtures, partial pressures, and effusion Each gas in air contributes its own share of pressure, and light molecules move faster, so they leak through a pinhole faster — the principle behind uranium enrichment. 20 min
- 4 Brownian motion: counting molecules under a microscope Why do particles from pollen never stop jiggling? Einstein tied their random walk to molecular motion, and Perrin, tracking grains one by one and counting them layer by layer under the microscope, obtained the Avogadro constant. Retrace his route with his own data, and meet an “atmosphere” inside a drop of water. 30 min
- 5 Real gases At high pressure and low temperature, molecular attraction and molecular size can no longer be ignored. The compressibility factor measures how far a gas is from ideal; the van der Waals equation explains why and predicts the critical point. 25 min