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This model demonstrates the phenomenon of osmosis on both small and large scale.

Press "Start". In the left-side window, you will see a stationary barrel filled with water, and a tube that contains a porous partition. You will also see a magnified representation of water molecules moving throughout the barrel.

As the experiment progresses, the tube begins to sink into the barrel, making it possible for the water molecules to pass into the tube through a porous partition. However, this reverse permeation is hindered by the presence of the solute (shown schematically in the model as pink oval formations), which cannot permeate the porous partition. This results in the direct movement of water molecules prevailing over their reverse movement. Net flow of water molecules into the tube increases, causing the water level in the tube to increase as well. The increase continues until the excess pressure in the tube equalizes the molecular flows.

This excess pressure is known as the osmotic pressure.

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