Separation of Substances - Part I

Dirt, stone and husk are big enough to be easily separated from pulses, rice, etc. by handpicking. 

Impurities in wheat vary in size. On the commercial scale, impurities like husk and stones are removed before grinding wheat by pouring it on a slanting sieve. This removes the pieces of stones, stalk and husk that may still remain after threshing and winnowing. So, apart from winnowing, the two methods are threshing and sieving. 

Winnowing is a method in which the heavier particles are separated from the lighter ones due to the difference in their weight. Separation of husk from grains is done using this method. 

Salt is soluble in water but sand is not. Sand being heavier settles at the bottom and can be separated by filtering the mixture. Salt and water can be separated by evaporation as water will evaporate leaving the salt behind. The water vapours can be collected by condensation. So, the methods involved in separating the mixture of sand, water and salt are filtration, evaporation and condensation. 

If we keep on adding a substance to water then a state arrives, when no more solute can be dissolved in it. Such a solution is said to be saturated, though more solute in the same can be dissolved by heating the solution. 

Decantation is a method used to separate a mixture of two liquids which do not mix with each other, and form different layers. Oil being lighter stays at the surface and water remains at the bottom, therefore the two can be separated by decantation. 

Evaporation refers to the conversion of a liquid into vapor state. A mixture of sugar and water can be separated by evaporation as water can evaporate but sugar can not.  

After harvesting, wheat or paddy stalks are dried in the sun and grains can be separated from the stalks by threshing. 

Evaporation refers to the conversion of a liquid to its vapour state. During evaporation, water changes from liquid to gas.

The mud in muddy water is heavier and settles down when this water is kept undisturbed for some time. The process is known as sedimentation. After this, the lighter impurities can be separated by the process of filtration. So, sedimentation followed by filtration can be used to purify muddy water. 

Churning of curd separates the butter; as butter is lighter. Tea leaves are big enough and can be easily separated using strainer. Also, stones are bigger in size than rice grains so they can be easily separated by hand picking. 

The substances which are made up of only one type of particles are known as pure substances. On the other hand, the substances made up of more than one type of particles are known as mixtures. Different components forming the mixtures are known as constituents. 

Stones are present as impurities in rice, thus decreasing the quality of rice. That is why stones need to be separated from rice. 

Churning refers to rotating a mixture at a high speed so that the lighter particles come at the surface and the heavier particles settle down. This method is used to separate cream from milk as cream being lighter comes to the surface and milk being heavier settles down. 

Winnowing is a method in which the heavier particles are separated from the lighter ones due to the difference in their weight. Separation of husk from grains is done using this method. 

At construction site, small and big stones are separated from the sand by a method called sieving. Sand passes through the sieve and pebbles and stones being larger get separated. 

Generally for the filtration process, things required are glass wool, filter paper and funnel. Cotton is not used for filtration. Funnel is glassware which holds the filter paper. Filter paper is a paper with small pores through which only things of particular size can pass. 

Paneer particles are bigger and can be separated by using a strainer. This process is known as filteration. 

Mixture is any substance which is made up of 2 or more types of particles e.g. sea water is a mixture of water and dissolved salts, air is a mixture of gases and water vapors, pickle is a mixture of oil, salt, spices etc. But common salt is a compound (NaCl) and not a mixture. 

A solid substance is not soluble and is heavier than the liquid. It will settle down at the bottom and the process is known as sedimentation. This process is helpful in removing impurities e.g. dust particles from rice as rice being heavier settle down and dust being lighter stays at the surface and can be easily removed. 

A solid substance is not soluble and is heavier than the liquid, it will settle down at the bottom and the process is known as sedimentation. This process is helpful in removing impurities e.g. dust particles from rice as rice being heavier settle down and dust being lighter stays at the surface and can be easily removed. 

Tea leaves are quite big in size so can be separated easily from the liquid using a sieve by the method of filtration.

Evaporation refers to conversion of a liquid into its vapour state and condensation refers to the conversion of vapours back to the liquid state. 

If we keep on adding a substance to water then a state arrives, when no more solute can be dissolved in it. Such a solution is said to be saturated, though more solute in the same can be dissolved by heating the solution. 

Evaporation refers to the conversion of a liquid into vapor state. A mixture of sugar and water can be separated by evaporation as water can evaporate but sugar cannot. Also, common salt is separated from sea water by the same process.