The Van der Waals Equation
This equation makes two corrections to the ideal gas law:
- + a·n²/V², corrects for intermolecular attraction reducing the measured pressure
- − nb, corrects for the excluded volume of the molecules themselves
Let's compare. On the right are two simulations running side by side.
Top: Ideal gas (no attraction, point particles)
Bottom: Real gas (attraction + finite size)
Note: Simulations may start with a brief spike in pressure. Give them a few seconds to stabilize.
Change the temperature using the + and − buttons below and see how the difference changes.
Cool the gas down.
At low temperature, the real gas pressure drops significantly below ideal; the attractions dominate. If you go cold enough, the real gas will start to condense into clumps!
Heat it up high.
At high temperature, the two pressures converge; fast-moving particles are barely affected by the weak attractions. Hot real gases behave nearly ideally.