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Indemnity4 t1_j3jbmy6 wrote

Reply to comment by Verneke in How much do water molecules move around within a stationary body of water? by KpgIsKpg

The self-diffusion coefficient of neat water is:

  • 2.3·10−9 m2·s−1 at 25 °C (room temperature, or close enough), and

  • 1.3·10−9 m2·s−1 at 4 °C (inside the fridge).

You can play around with equations for diffusion towards a target (on average a straight line velocity), diffusion over a certain distance (e.g. how long to randomly move from one wall to the opposite side), or collision frequency.

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