TNPSC Science Notes - 6th Standard - Separation of Substances

6th Standard - Science - Separation of Substances 2

The different methods of separation we adopt in our daily life.

Winnowing

Lighter particles present in a mixture can be separated by winnowing. The method of separating lighter particles from heavier particles with the help of wind is called winnowing. Farmers allow the mixture of grain and husk to fall from a height. Grains, being heavier fall down and form a heap. Husk, being lighter is carried away by wind and forms a separate heap.

Sieving


Components of a mixture can be separated by the method of sieving only when they differ in their size. At construction sites, you would have seen the separation process of pebbles and stones from sand. It is done by sieving using a sieve.


Magnetic Separation


Magnetic separation is used to separate mixtures containing components, which are attracted by a magnet. 

Methods of separation of insoluble solids from liquids

We can separate insoluble solids from liquids by using the method of sedimentation, decantation and filtration.

Sedimentation

The mixture of insoluble solids and liquid is taken in a beaker and the solid subtances are allowed to settle down as sediments. This is known as sedimentation. The clear liquid above the sediment is called supernatant liquid. e.g. a mixture of sand and water

Filtration

Take a filter paper and fold it like a cone. Fix it inside a glass funnel. Fix the funnel on a stand and place a beaker below it. Pour the impure liquid containing suspended impurities into the funnel. The liquid drains through pores of the filter paper. The clear liquid that is collected in the beaker is known as filtrate. The dust particles that remain on the filter paper is called "residue".

Methods of separation of solid substances dissolved in liquids

Evaporation and condensation processes are used to separate solid substances dissolved in liquids.

Evaporation

Evaporation is a process in which a liquid changes into vapour on heating. Evaporation method is used to separate dissolved solids from liquids.

Condensation


Filter this solution using a filter paper. The sand can be separated from the salt solution by filtration. Set up the apparatus as shown in the picture. Take the salt solution in ba conical flask and heat it strongly. The water vapours pass through the delivery tube and get collected in a test tube. The test tube is placed inside a pack of ice cubes. The water vapours get cooled and condense into water. The salt remains as residue in the conical flask, once all the water gets evaporated. When the vapours of a substance get cooled, they condense into liquid. This process is known as condensation.

Important Questions and Answers in the lesson

I. Choose the correct answer:


1. A suitable method to separate lighter impurities from a mixture is _____.
a) winnowing 
b) hand picking
c) evaporation 
d) magnetic separation

Answer: a) Winnowing

2. In a mixture, solids of different sizes can be separated by _____?
a) magnetic separation 
b) winnowing
c) sieving 
d) evaporation

Answer: c) sieving

3. The method used to separate seeds from fruit juice is _____?
a) filtration 
b) sieving
c) crystallization 
d) winnowing

Answer: a) filtration

4.Separation of common salt from the sea water is done by _____?
a) sieving b) evaporation

c) magnetic separation 

d) winnowing

Answer: b) evaporation

5. The method used to separate substances that differ in colour, size and shape from a solid mixture is _____.
a) magnetic separation 
b) decantation
c) hand picking 
d) sieving

Answer: c) hand picking

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