Question

Explain why Oil does not mix in water. However, oil and water become homogeneous if a sufficient quantity of detergent is added.

Answer 1

Hint: When two or more liquids are mixed with each other but are immiscible, then the mixture is called emulsion. A homogenous mixture is a mixture where the concentration of solute is equally distributed throughout the solvent. An example would be salt in water.

Complete step by step answer:
An emulsion can be defined as a mixture of two or more than two liquids that are usually immiscible and formation of liquid-liquid phase separation takes place. Emulsions are part of a wider class of systems containing two-phases of matter termed as colloids. Although the terms emulsion and colloid could be sometimes used interchangeably, emulsion must be used when both phases under consideration, that is dispersed and continuous phase, are liquids. In case of an emulsion, one of the liquid which acts as the dispersed phase, is dispersed in the other liquid which is acting as the continuous phase. Some common examples of emulsions include homogenized milk, biomolecular condensates, vinaigrettes, liquid etc.
Two liquids which we are considering, can form various types of emulsions. For instance, at first oil and water may form an oil-in-water emulsion. In this kind of emulsion, the oil is the dispersed phase, and water is the continuous phase, this is because the amount of oil is much lesser than the amount of water. Second, it may form a water-in-oil emulsion, in which water is the dispersed phase and oil will be the continuous phase. Multiple forms of emulsions are also probable, including a "water-in-oil-in-water" emulsion and an "oil-in-water-in-oil" emulsion.
As per the question, oil and water are two immiscible liquids meaning they would repel one another naturally. But when we add some amount of detergent to a solution which is containing water and oil, the mixture is converted to a homogeneous form. This occurs because of the molecule of detergent. The molecules of detergent consist of two ends. One of its ends holds on to an oil molecule and the other end holds on to the water molecule. These opposing forces are responsible for dissolving the oil in water and thus producing a homogeneous mixture.

So, the correct answer is Option A.

Note: 1.The mixture of oil and water becomes homogeneous as detergent is added to it, this is because of the hydrophilic and hydrophobic tails of the detergent.
2.The hydrophilic part attracts the water molecules, and the hydrophobic part repels it and attracts the oil molecules. This is the sole reason the detergent is more efficient in removing dust and dirt from clothing, as the dirt also contains some oily substances which the hydrophobic part will hold.
Examples of emulsions can be observed in Lipids, used by all living organisms.