Thermodynamics
Isobaric heating
Heat at constant P: the gas expands and does work.
Isobaric heating — interactive Thermodynamics simulation. Heat at constant P: the gas expands and does work. Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Isobaric heating
Heat at constant P: the gas expands and does work.
At constant pressure, heating an ideal gas forces expansion so the gas can do work on the surroundings while temperature rises. From the first law, Q = ΔU + W; part of the absorbed heat lifts internal energy and part pays for expansion work.
- W = PΔV
- Q = ΔU + W
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
A gas is heated at constant pressure, so it expands (isobaric). If you let it expand to a larger final volume, does the gas do more work on its surroundings?
Predictions to weigh
- A larger final volume means less work done by the gas.
- Work done doesn't depend on the final volume.
- A larger final volume means more work done by the gas.
Variable roles
What you set:
- Final volume V₂ (L)
What you measure:
- Work done by gas W_gas (J)
- Final temperature T₂ (K)
How the investigation runs
- Open the isobaric-heating preset and press Reset. 1 mol of gas starts at 24.9 L, 300 K, at constant pressure.
- Enable the final-temperature readout on the chamber.
- Set the target (final) volume for each trial, and record the final temperature and the work done.
Governing equation
Isobaric Work — W = P·ΔV
At constant pressure, the work done by an expanding gas is simply pressure times the volume change: W_gas = P·ΔV — the area of a rectangle under a horizontal line on a P-V diagram.
What the printable worksheet asks students to work out
- For one trial, compute W_gas = P₁(V₂ − V₁) using P₁ = nRT₁/V₁ = 100 kPa, then T₂ = T₁·V₂/V₁. Compare both to the table.
- Explain, using W_gas = P·ΔV, why a bigger volume change at the same constant pressure means more work done by the gas.
Where this shows up beyond the lab
- Your T₂-vs-V₂ line is Charles's Law: at constant pressure, volume and absolute temperature are directly proportional. Explain why this follows directly from PV = nRT when P is held fixed.
- Some of the heat you add during isobaric heating goes into work (expansion) and some into internal energy. Which one gets more of the added heat for a monatomic gas (f = 3): the work term or the internal-energy term?
- AP Physics 2 — Unit 9: Thermodynamics
- IB Physics — B.4 Thermodynamics
- General High School Physics — Heat, temperature & gas laws
- NGSS High School Physics — Thermal energy transfer
- Welcome to Isobaric Heating
- Select the chamber
- Press Play
- Heating at constant P
- Open the Properties panel
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.