Why does shaking affect the rate of dissolution?
There are three main reasons why stirring could affect the rate of dissolution. For our initial system, let’s use a beaker with, let’s say, a half inch layer of sugar on the bottom and filled most of the rest of the way with fresh, room temperature water. With no stirring that layer of sugar is just going to sit on the bottom. If you look very closely at the interface between liquid and solid, you can actually see some of the sugar dissolving. There will be fluid veins of different densities and will reflect light at slightly different angles (see fluid dynamics for more information http://en.wikipedia.org/wiki/Fluid_dynamics). Left alone, diffusion alone is left to make the solution uniform and since sugar water is denser than pure water, diffusion also has to overcome gravity. Stirring increases the rate of diffusion and will increase the rate of dissolution. Another important factor is surface area. The top of a thick layer of sugar has moderate to decent access to the water that is
