Physic Labs

Thermal physics

Gas laws

Explore ideal-gas states on a p–V plot while changing T, V, n. Verify pV=nRTpV = nRT and the three special laws: isothermal pV=constpV = \text{const}, isobaric V/T=constV/T = \text{const}, isochoric p/T=constp/T = \text{const}.

High school

⚠ Virtual simulation; with real gases, never over-compress or overheat a sealed vessel — rising pressure can burst it.

Equipment

  • Virtual gas cylinder with piston on a p–V plot
  • Sliders for temperature T, volume V, and amount n
  • Three process buttons: isothermal, isobaric, isochoric
  • Readout line for initial and final states

Procedure

  1. Isothermal process

    Press the Isothermal button and drag the volume slider V: temperature is locked, pressure varies inversely with V. Record two (V, p) pairs from the readout; check that the product pVpV stays constant — the curve is the hyperbola p=nRT/Vp = nRT/V.

  2. Isobaric and isochoric processes

    Choose Isobaric: raising T makes the piston expand while p stays constant — verify V/T=constV/T = \text{const} (T in kelvin). Choose Isochoric: V is locked, vary T and read p, verifying p/T=constp/T = \text{const}. The dashed line on the plot joins each process's initial and final states.

  3. Change the gas amount and predict

    Increase the amount n at fixed T, V: pressure must rise proportionally via p=nRT/Vp = nRT/V. Before moving the slider, predict the new pressure, then compare with the readout; try finding the n that doubles p for a given state.

Simulation

Experiment history

In 1662 Robert Boyle published the relation pV=constpV = \text{const} measured on air compressed in a J-tube. Jacques Charles studied gas expansion with temperature in the 1780s (unpublished), and Joseph Louis Gay-Lussac measured that law quantitatively in 1802. In 1834 Émile Clapeyron combined the results into pV=nRTpV = nRT. Amedeo Avogadro (1811) added the notion of amount: equal V, p, T imply equal molecule counts for any gas. William Thomson (Lord Kelvin) proposed the absolute temperature scale in 1848, building on Carnot's work — the condition that lets the gas laws take simple proportional forms.

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