Physics
Ideal gas
Heat, compress and expand an ideal gas and see how molecular motion shows up as temperature, pressure and volume.
Launch simulationHow it works
Temperature measures the average kinetic energy of the molecules, and pressure comes from their collisions with the walls. An ideal gas obeys the equation of state p·V = n·R·T. At constant volume (isochoric) pressure rises in proportion to temperature, at constant temperature (isothermal) pressure is inversely proportional to volume, and at constant pressure (isobaric) volume grows in proportion to temperature. The root-mean-square speed of the molecules grows with the square root of temperature.
p·V = n·R·Tv_rms = √(3·R·T / M)U = 3/2 · n·R·T
Try it yourself
- The starting state is 1 mol of argon at 300 K in 25 L. The pressure is 99.8 kPa and the root-mean-square speed is 433 m/s.
- With “Volume · isochoric process”, raise the temperature to 600 K. Predict first: the pressure doubles to 199.5 kPa, but the molecular speed rises only √2 times, to 612 m/s.
- Switch to “Temperature · isothermal process” and halve the volume to 12.5 L. The pressure doubles while the molecular speed stays the same.
- In the “Your experiment, traced” chart, compare the shape of an isotherm (a hyperbola) with an isobar (a horizontal line) in the p–V diagram.
Model limitations
The simulation shows an ideal gas: molecules are points that do not attract each other, collisions are perfectly elastic and the animation shows only a small sample of particles. Real argon would liquefy below 87 K at atmospheric pressure. The “States of matter” tab only compares particle arrangements; it does not calculate phase changes.