Oil / Water Simulations
(1) Simulation of Separated Oil and Water
In this simulation, pure water (red and white sticks) on the left is
placed next to pure oil (octane; grey) on the right.
The length of the rectangular box shown is 13 nm.
Over the course of 0.5 nanoseconds, the two substances remain separated, in agreement with our
everyday experiences.
As explained above, the water molecules are attracted to one another
primarily through electrostatic attractions. According to
electronegativity
difference values, the carbon-hydrogen bonds in the
oil molecules are only very weakly polar, and the resulting oil-oil
electrostatic attractions are very small compared to those in water.
In fact, the primary attraction between the oil molecules is due to
London dispersion forces.
There is a small attraction between the separated charges in water
molecules with the induced dipoles in the oil molecules. This small
attraction gives rise to the short-lived mixing at the
water-oil interface that may be able to be seen in the simulations.
(2) Separation of Oil/Water Mixture
Water and oil (octane)
in an initally mixed state undergoes separation
into pure water and pure oil over the course of 0.5 nanosseconds.