Gas pressure and temperature
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What this model shows
50 cm³ of air is trapped in a gas syringe joined to a pressure gauge by a thin tube; no air gets in or out. The gauge shows the whole pressure of the air, so 0 kPa would mean no hits at all, a vacuum; the air around us is at 100 kPa. The air in the tube, about 1 cm³, is left out.
The readings follow the ideal-gas rule: the pressure doubles when the volume halves, and it rises in step with the temperature in kelvin (p = 100 kPa × (50 cm³ ÷ V) × (θ + 273) ÷ 293). Air at these pressures and temperatures behaves almost exactly like this. A real syringe leaks a little and its plunger sticks; this one does not.
Squeezing the air warms it a little for a moment, so the needle overshoots and then settles as the water takes the warmth away. Warming and cooling the water are shown sped up: a real beaker of water takes minutes.
The magnifier is a model: 12 particles stand for billions of billions, drawn far bigger than real. How much faster they move when warmer is exaggerated four times, so that you can see it.
With reduced motion each step is drawn complete at once and the particles in the magnifier stand still.
Select equipment to read its description in the card.