Final answer:
Upon violent shaking of oil with water, the non-polar oil droplets disperse in the polar water, forming an emulsion. An emulsifying agent such as soap can stabilize the emulsion by preventing the oil droplets from coalescing.
Step-by-step explanation:
When oil is violently shaken with water, at the molecular level, the oil, which is pure hydrocarbon and non-polar, breaks up into smaller droplets. These droplets are then dispersed in the water, forming an emulsion.
However, without an emulsifying agent, such as soap, these droplets tend to coalesce back together due to the non-polar nature of oil and the polar nature of water. If an emulsifying agent is present, the non-polar hydrocarbon tail dissolves into the oil while the polar head orients towards the water. This creates a charged surface around each droplet that prevents them from coming together, keeping them suspended in the water and allowing the mixture to be washed away.