[paul.fr]

another question reminded me of this. Say you have a sugar and water solution, no stirring will make the sugar dissolve quite slowly, but give it a good stir and it dissolves quicker. Why?

[lightarrow]

another question reminded me of this. Say you have a sugar and water solution, no stirring will make the sugar dissolve quite slowly, but give it a good stir and it dissolves quicker. Why?

Essentially for the same reason that clothes dries faster when there is wind than whith calm air (if the wind it's not very cold, of course!): sugar's molecules just dissolved increases the concentration of the solution near the  solid sugar and this slows the dissolution of the solid; with stirring you mix the concentrated solution with the diluted solution, increasing the dissolution because now the solid have around it a more diluted solution (that is, more water).

With a drying cloth is the same: water vaporize and so increases the vapour pressure in the athmosphere around the cloth, decreasing the water vaporization speed.