Third law of thermodynamics
Chemical Thermodynamics · Chemistry
Gas piston lab
Interactive 3DHeat the gas and watch molecules speed up — pressure obeys the gas laws live.
Controls
Drag the sliders or type a value — the simulation updates live.
K
200K600K
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0.5×2×
Study notes
Why can't we reach 0 K? Use the third law. Step 1: Third law: perfect crystal at 0 K has exactly one microstate → S = 0. Step 2: Cooling needs heat removal; each step removes less as C_P → 0. Step 3: Infinite steps needed to remove the last bit — like halving distance to a wall. Step 4: Record: ~38 pK (picokelvin) in labs — close, never zero. Absolute zero is thermodynamics' unreachable horizon.