Chapter 3: Separation of Substances

When two or more substances are mixed together, they form a mixture. Components of a mixture should be separated because some components may not be useful or may spoil the useful component of the mixture.

Examples:

Tea leaves are separated from the liquid with a strainer while preparing tea.

Removal of stone pieces from wheat, rice or pulses by hand.

The method of separating the components from a mixture is known as winnowing. In this method, heavier and lighter components of a mixture are separated by wind or by blowing air. This method is used by farmers to separate lighter husk particles from heavier seeds of grain.

Husk and dirt particles are separated from pulses by winnowing.

Sieving is a method in which fine particles are sieved through holes in the sieve while the bigger impurities remain on the sieve. Sieving is used in a flour mill to separate impurities like husk and stones from wheat before grinding it. It is also used at construction sites to separate pebbles and stones from sand.

Sand and water are separated from their mixture by the following steps:

a) The mixture is allowed to stand without any disturbances.

b) Now, sand settles down.

c) Slowly pour the water into another container to obtain sand in the bottom.

Yes, it is possible to separate sugar mixed with wheat flour by the following method:

a) Mix sugar and wheat flour in water.

b) Stir the solution to allow the sugar to dissolve.

c) Now, filter the mixture.

d) Filtrate contains the sugar solution, and the residue will be wheat flour.

The following process should be carried out to obtain clear water from muddy water:

i) Allow muddy water to stand.

ii) Mud gets settled down in the water.

ii) Slowly pour water into another container.

(a) The method of separating the seeds of paddy from its stalks is called threshing.

(b) When milk cooled after boiling is poured onto a piece of cloth, the cream (malai) is left behind on it. This process of separating cream from milk is an example of filtration.

(c) Salt is obtained from seawater by the process of evaporation.

(d) Impurities settled at the bottom when muddy water was kept overnight in a bucket. The clear water was then poured off from the top. The process of separation used in this example is called decantation.

a) False

b) False

c) False

d) False

Ice should be added to lemonade after dissolving sugar. It is possible to add more sugar before adding ice.

Chapter 6 of NCERT Class 6 Science introduces students to the methods of separation, such as hand-picking, winnowing, threshing, sieving, sedimentation, decantation, filtration and evaporation. The NCERT Solutions for Class 6 Science of this chapter will make them understand the process of separation by using real-life examples, such as separating husks and stones from grains, separation of solids from liquids etc.