Question

why we pour lycopodium powder on water to determine the size of oleic acid molecule

Answer 1

Oleic acid molecules consist of two parts, one is "water loving" (hydrophilic) or polar portion and other is "water fearing" (hydrophobic) or nonpolar portion.When added to water, they spread out on the surface in a layer that is one molecule thick (a monolayer), with the hydrophilic portion bound to the water surface, and the hydrophobic portion pointed away from the water. Lycopodium powder is used to distinguish between area covered by oleic acid and without oleic acid.The lycopodium powder does not cover the surface occupied by the oleic acid. ​After the system has stabilized measure the diameter of the circle that is powder-free. In this way by calculating the volume and area we can find-out the length of oleic acid using lycopodium powder.