Entropy is spreading out
"Entropy is spreading out" is a free, interactive Class 11 Chemistry simulation for NEET and JEE, built on the NCERT section "Spontaneity and entropy" in Thermodynamics. Particles in a two-chamber box: lifting the partition lets them spread, a counter shows the number of arrangements W and ΔS = nR ln(V2/V1) while q = 0; a second mode adds heat q at low or high T for ΔS = q/T. NEET has asked about this idea 5 times in 10 years of papers. JEE Main asked 51 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Spontaneity and entropy in Thermodynamics. Change the values and watch what happens.
What it shows
NCERT § "Spontaneity"
Particles in a two-chamber box: lifting the partition lets them spread, a counter shows the number of arrangements W and ΔS = nR ln(V2/V1) while q = 0; a second mode adds heat q at low or high T for ΔS = q/T.
Controls
4 to try
- Buttonremove partition (free expansion)
- Slidervolume ratio V2/V1 1–4
- Segmentedphase solid / liquid / gas
- Sliderheat added 0–5 kJ at T 100–1000 K
Try this
Double the volume by free expansion of 1 mol and read ΔS = 5.76 J/K with q = 0; then find which temperature makes the same 1 kJ give the larger ΔS.
Common mistake
Free expansion has ΔS = 0 because q = 0; entropy of a gas does not depend on volume.
In NEET
10 years of papers
Asked 5 times in 10 years of NEET.
See the past questions: Gibbs Free Energy, Thermodynamics (chapter)
In JEE Main
42 shifts analysed
51 questions from Thermodynamics across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "Spontaneity"
- A spontaneous process can proceed on its own without outside help once started; spontaneity says nothing about how fast it happens.
- A negative ΔH favours spontaneity but does not guarantee it: some endothermic processes, such as dissolving certain salts, are spontaneous.
- Entropy S measures the degree of randomness or disorder of a system; it is a state function.
- Entropy increases from solid to liquid to gas, on dissolving a solid, and generally when a reaction produces more gas molecules.
- For a reversible transfer of heat q_rev at temperature T, ΔS = q_rev/T; the same amount of heat raises entropy more at low temperature than at high temperature.
- A process is spontaneous when the total entropy change is positive: ΔS_total = ΔS_sys + ΔS_surr > 0.
- At equilibrium ΔS_total = 0.
- For an isolated system ΔU = 0, and entropy is the driving force: ΔS > 0 for a spontaneous change.
- Third law: as the temperature approaches 0 K, the entropy of a pure, perfectly crystalline substance approaches zero. Solutions and supercooled liquids keep some entropy at 0 K. The law lets absolute entropies of pure substances be worked out from thermal data.
Questions
5 answers
- What does the "Entropy is spreading out" simulation show?
- Particles in a two-chamber box: lifting the partition lets them spread, a counter shows the number of arrangements W and ΔS = nR ln(V2/V1) while q = 0; a second mode adds heat q at low or high T for ΔS = q/T.
- What mistake does the "Entropy is spreading out" simulation fix?
- A common mistake it clears up: free expansion has ΔS = 0 because q = 0; entropy of a gas does not depend on volume.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 5 times in 10 years of papers.
- Does JEE Main ask questions from Thermodynamics?
- Yes. JEE Main asked 51 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Spontaneity and entropy" in Thermodynamics (Class 11 Chemistry).
Embed this simulation
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