I'm having a status just so I don't have no status
- Jan 13, 2019
- Reaction score
- Brisbane, Australia
Soap emulsifies the oil and keeps it floating in the water in very small droplets.This is the moment where I wonder quietly and briefly what an oil-attacking dish soap actually does to the oil...
Oil is hydrophobic because it doesn't have any charged portions on its molecules. In contrast, each water molecule has a positively and negatively charged side; the differently-charged ends of the water molecules attach themselves to other molecules that also have a charge and, in the case of salts, even wedge themselves into the crystals to separate the salt into ions.
Water is such a good and universal solvent (other than for fats and oils) because many substances also have an unevenly-distributed electric charge on their molecules. The water molecules attach themselves with their positive side to the negative side of what they dissolve (or vice versa), and then the water molecules attach to each other by linking up opposite charges. The net effect is that the substance ends up in solution because individual molecules are "carried" by the water molecules.
Soap molecules have no charge at one end, but do have a charge at the other end. The uncharged ends align with the oil, and the charged ends align with water molecules. You can think of soap molecules almost as a bridge that likes to stick to fatty things at one end, and to watery things at the other end.