Pure Substances and Mixtures; Separation of Mixtures Test - 1

Handpicking is the method of separating large sized impurities from the mixture by hand. Stones are large sized impurities and can be separated from the mixture of rice and stones by handpicking.

A homogeneous mixture consists of only one phase. This single phase may be gaseous, liquid, or solid.

The correct answer is A.

Why alternative B is wrong:

A homogeneous mixture consists of only one phase. However, it is not necessarily liquid. It can be solid or gaseous also.

Why alternative C is wrong:

A mixture that has two or more phases is known as a heterogeneous mixture.

Why alternative D is wrong:

A homogeneous mixture consists of only one phase.

Distillation is used for separating mixtures having appreciable difference in their boiling points. The mixture can contain two liquids, but the liquids should not decompose on boiling.

Thus, both Shruti and Mona are correct.

Ammonium chloride is a sublimable and volatile substance. Salt, on the other hand, is non-sublimable. When a mixture containing the two is heated at a high temperature, ammonium chloride gets converted directly into gas (ammonia), leaving behind salt. The conversion of a solid directly into gas is called sublimation.

Mixtures are formed when two or more substances are mixed in any proportion. Therefore, a mixture displays the chemical properties of all its components. However, the physical properties of a mixture such as melting point, boiling point etc. may differ from those of its components. For example, the melting point of brass is in the range of 900-940 K, while that of its components, i.e., copper and zinc is 1357 K and 692 K respectively. Also, the components of a mixture can be separated using physical methods.

The correct answer is C.

Two liquids are said to be immiscible if they arrange themselves in layers when mixed in any proportion. Oil and water are immiscible liquids.

Sieving allows only fine particles to pass through the holes of a sieve, while the bigger substances remain on it. Sand particles are fine enough to pass through the sieve, while pebbles will remain in the sieve itself.

Husk is removed from grain seeds by winnowing. Winnowing can be employed to separate heavier and lighter components of a mixture by wind. The heavier grain seeds get collected in the form of a heap near the winnowing platform, while the lighter husk particles are carried away by the wind.

Brass is an alloy of copper and zinc. These two metals cannot be separated by physical methods as they exist in a single phase. Hence, brass is an example of a homogeneous mixture of metals.

The correct answer is D.

Why alternative A is wrong:

The mixture of iron and calcium is a heterogeneous mixture as iron and calcium can be separated by the application of a magnetic force.

Why alternative B is wrong:

The mixture of iron and copper is a heterogeneous mixture as iron and copper can be separated by the application of a magnetic force.

Why alternative C is wrong:

Iron, existing in its pure form, is an element, and not a mixture.

Decantation is the process of separating a mixture of two immiscible liquids. Kerosene and water are two immiscible liquids. In the mixture of water and kerosene, water settles down and kerosene being lighter forms the top most layer of the mixture. Therefore, by the method of decantation, kerosene and water can be separated.

According to the particle theory, a pure substance implies that it does not contain any type of impurity in it. Pure substances are made of the same kind of atoms. Hence, pure substances comprise identical particles.