When you add oil to water, the two liquids will not mix. Oil is a nonpolar molecule, while water is a polar molecule. This means that oil and water do not have any attraction for each other. As a result, the oil will float on top of the water.

If you then add an emulsifier to the mixture and shake it, the emulsifier will help to disperse the oil droplets throughout the water. This is because emulsifiers are molecules that have both hydrophilic (water-loving) and hydrophobic (water-hating) ends. The hydrophilic ends of the emulsifier molecules will attach to the water molecules, while the hydrophobic ends will attach to the oil molecules. This will cause the oil droplets to break up into smaller droplets and become suspended in the water.

The resulting mixture is called an emulsion. Emulsions are unstable mixtures, and the oil droplets will eventually separate from the water. However, the emulsifier can help to slow down this process by preventing the oil droplets from coalescing.

Emulsions are used in a variety of products, including salad dressings, mayonnaise, and ice cream. They are also used in some pharmaceutical products.