Chemistry / Unit 7 Chem 1294 short lesson, about 20 seconds
Effusion
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The idea
Effusion is the escape of gas molecules through a tiny opening into a vacuum, one molecule passing through at a time.
In practice
Helium leaks out of a pinhole-punctured balloon faster than the surrounding air leaks in, since effusion favors lighter molecules.
Where people slip
Effusion is diffusion's narrower cousin: diffusion spreads through open space, while effusion specifically crosses a small opening into a vacuum.
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