Question

Which of the following is not an emulsion?
A. Milk
B. Cold cream
C. Butter
D. Shaving cream

Answer 1

Hint : An emulsion is a mixture of two or more liquids that are normally immiscible (unblendable or unmixable) due to liquid-liquid phase separation. Emulsions are a type of colloids, which are a more general class of two-phase matter systems.

Complete Step By Step Answer:
Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both phases are liquids, dispersed, and continuous. One liquid (the dispersed phase) is dispersed in the other in an emulsion (the continuous phase). Vinaigrettes, homogenized milk, liquid biomolecular condensates, and some metalworking cutting fluids are examples of emulsions.
Different types of emulsions can be formed by combining two liquids. Oil and water, for example, can form an oil-in-water emulsion, in which the oil is the dispersed phase and the water is the continuous phase. Second, they can form a water-in-oil emulsion, in which the dispersed phase is water and the continuous phase is oil. Multiple emulsions, including a "water-in-oil-in-water" emulsion, and an "oil-in-water-in-oil" emulsion.
Option A: Milk: Milk is an emulsion that contains fat particles (globules) that are dispersed in an aqueous (watery) environment. Because the fat globules are protected by a membrane layer that separates the fat particles from the water phase, they do not coalesce and form a separate layer (oil off or churn).
Option B: Ice cream: Ice cream is an emulsion, which is a mixture of two liquids that do not normally mix. Instead, one of the liquids is mixed with the other. Liquid fat particles, known as fat globules, are distributed throughout a mixture of water, sugar, and ice, along with air bubbles, in ice cream.
Option C: Butter: Butter is an emulsion in and of itself. This emulsion breaks when butter is heated and begins to melt — the butterfat naturally separates from the milk solids and water.
Option D: Shaving cream: Shaving cream. The colloidal solution is made up of two parts: dispersing phase and dispersing medium. Because shaving cream is a foam, it is not an emulsion.
Emulsions are classified into two types: oil-in-water (O/W) and water-in-oil (W/O). Because shaving cream is a foam, it is not an emulsion.
Thus, the answer is option D: Shaving cream.

Note :
The photo-sensitive side of photographic film is also referred to as "emulsion." A photographic emulsion of this type is made up of silver halide colloidal particles dispersed in a gelatin matrix. Nuclear emulsions, like photographic emulsions, are used in particle physics to detect high-energy elementary particles.