# What is the form of science behind how the surface area affects the dissolving rate?I get that the more exposed it is the faster it dissolves but I am confused as to what causes this for example...

What is the form of science behind how the surface area affects the dissolving rate?

I get that the more exposed it is the faster it dissolves but I am confused as to what causes this for example what is causing it to do this e.g. when you bounce a ball it is because of kinetic energy e.c.t

trophyhunter1 | College Teacher | (Level 1) Educator Emeritus

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Surface area affects the rate at which a substance dissolves. More surface area means that the molecules can move about in a greater area, resulting in more collisions between molecules, speeding up dissolving time. This has to do with Collison theory.When you experiment between the dissolution rate of powdered sugar, granulated sugar and sugar cubes in the solvent water, the powdered sugar dissolves fastest. This is because by grinding the sugar into the smallest particles, this increases its surface area allowing it to dissolve faster.

The surface area you are referring to is where the dissolving substance and the solvent meet. The rate of dissolution can be expressed by the following equation--

dm/dt= A D/d (Cs-Cb)

In this equation, m is the amount of dissolved material expressed in kilograms. Time  or t, is measured in seconds. A refers to the surface area. D is the diffusion coefficent. The higher the Diffusivity, the faster one substance diffuses into another. Lower case d represents the thickness of the boundary layer between the solvent and the top of the dissolving substance. Cs is the concentration in kg/m3 of the  substance found at the surface and Cb is the concentration of the bulk of the solvent in kg/m3.

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