Question

A mixture of ammonium chloride and sand is best separated by

• A. handpicking
• B. winnowing
• C. sieving
• D. sublimation

Answer 1

The correct option is D

sublimation

The explanation for the correct answer

(D) sublimation

• The change of matter from solid to gaseous state directly without converting into liquid is called sublimation.
• Solids such as ammonium chloride, iodine, naphthalene, and camphor are examples of sublimation.
• When a mixture of ammonium chloride and sand is heated, ammonium chloride sublimes from solid to gas, and sand is left behind.
• Therefore, sublimation is used to separate a mixture of ammonium chloride and sand.

The explanation for the incorrect answer

(A) handpicking

• Handpicking is used for removing undesirable solid constituents from a mixture.
• The differentiating property is a difference in the physical appearance of the components such as shape, color, and size.
• Example: Separating different colored flowers in a vase, Picking out apples in an area.
• This method is not possible to separate ammonium chloride and sand because there is no difference in the size of the components.

(B) winnowing

• Winnowing is the process of separating light solid particles from heavier solids by dropping slowly from a height in the presence of wind.
• Wheat is separated from husk by using the winnowing method.
• The differentiating property is the difference in weight of the components but the mixture of ammonium chloride and sand does not belong to this property because both the components are the same weight.

(C) sieving

• Sieving is a method of using a sieve to distinguish small particles from bigger particles. It is used in flour mills or building sites. Impurities such as husks and stones are extracted from wheat at the flour mill. They remove pebbles and stones from sand through sieving.
• The differentiating property is a difference in the size of the components but the mixture of ammonium chloride and sand does not belong to this property because both the components are of the same size.
  

Hence, the correct option is (D).