Exercises of topic 6 of the Thermodynamics course page (Termodinamika, 6. gaia, ariketak), each one an interactive page: the apparatus drawn and set in motion from the physics rather than by hand, the states in the p–V plane, the energy and entropy balance as it is generated, and a switch or two that go beyond the statement. Every page has an EN | EU toggle, and every formula is typeset. A balance can be hidden until the class is ready for it.
MethodNothing on a page is eased by hand: a wall swings because the gases push it, a load bobs because a cord is elastic, two gases mix because they diffuse. The balances use only the statement's numbers and the state functions.
CheckedEvery number is recomputed when the site is built, and each page's own script is run outside the browser against the same models.
Oxygen and nitrogen in a rigid adiabatic vessel: the wall between them made diathermal and movable, or removed; the entropy generated as it happens, 0.81 or 9.04 J/K; with the same gas on both sides the second case has nothing to show.
The entropy change computed the way it is calculated: a double free expansion, thermal contact, then superposition; the gases as material points that never collide with each other; the Gibbs correction for one gas; a switch gives the two gases equal amounts.
The free expansion of a real gas in contact with a reservoir at 300 K, and the reversible isotherm that undoes it; a load on the piston shows what changes when the expansion is made to lift something.