Unit Test (Solution): Methods of Separation in Everyday Life | Science for Class 6 PDF Download

Attempt all questions. 
Time: 1 hour
M.M. 30

• Question numbers 1 to 7 carry 1 mark each.
• Question numbers 8 to 12 carry 2 marks each.
• Question numbers 13 to 15 carry 3 marks each.
• Question number 16 carries 4 marks each.

Q1: The method of separating small stones and husk from grains by picking with hands is called __________. (1 Mark)
Ans: handpicking

Handpicking is based on differences in size, colour, and shape of particles when unwanted components are present in small quantities.

Q2: The process of beating stalks to separate grains from them is known as __________. (1 Mark)
(i) Winnowing
(ii) Threshing
(iii) Sieving
(iv) Filtration

Ans: (ii) Threshing

Threshing involves beating harvested stalks on a log to loosen grains, as observed by Malli and Valli in the fields.

Q3: Separating heavier grains from lighter husk using wind or blowing air is called __________. (1 Mark)
Ans: winnowing

Winnowing uses a bamboo tray (soop) to allow wind to blow away the husk while grains fall straight down.

Q4: The method used to separate bran from wheat flour based on particle size is __________. (1 Mark)
(i) Evaporation
(ii) Sieving
(iii) Decantation
(iv) Churning

Ans: (ii) Sieving

Sieving allows fine flour to pass through holes while larger bran and stones remain on the sieve.

Q5: Obtaining salt from seawater by allowing water to evaporate in sunlight is an example of __________. (1 Mark)
Ans: evaporation

Evaporation converts liquid water to vapour, leaving solid salt behind in shallow pits.

Q6: The settling of heavier tea leaves at the bottom of tea before pouring is called __________. (1 Mark)
(i) Filtration
(ii) Sedimentation
(iii) Magnetic separation
(iv) Handpicking

Ans: (ii) Sedimentation

Sedimentation causes heavier insoluble components to settle at the bottom of a liquid.

Q7: Separating iron nails from sawdust using a magnet is an example of __________. (1 Mark)
Ans: magnetic separation

Magnetic separation uses a magnet to attract magnetic substances like iron from non-magnetic ones like sawdust.

Q8: Explain briefly how threshing helps farmers prepare grains for storage or cooking. (2 Marks)
Ans: Threshing is the process of beating harvested stalks on a wooden log to separate grains from the stalks. This loosens the grains, allowing them to be collected easily, as seen when farmers in Haryana worked while singing folk songs. It ensures grains are free from stalks for further processing like winnowing.

Q9: Why is winnowing not effective in a closed room without wind? (2 Marks)
Ans: Winnowing relies on wind or blowing air to separate lighter husk from heavier grains by carrying the husk away while grains fall down. In a closed room, there is no natural air flow, so the components cannot be separated effectively, as Valli experienced while trying to separate husk from rice.

Q10: Describe the role of a sieve in preparing wheat flour for cooking. (2 Marks)
Ans: A sieve is used to separate fine flour particles from larger bran and small stones. The fine particles pass through the uniform holes, while bigger ones remain on top. This ensures the flour is clean and suitable for dishes like meethi puri, as Mami explained to Valli.

Q11: How does decantation differ from filtration? (2 Marks)
Ans: Decantation involves gently pouring off a liquid from a settled solid, while filtration involves passing a liquid through a filter to separate insoluble solids.

Q12: Differentiate between sedimentation and decantation with an example from tea preparation. (2 Marks)
Ans: 

Q13: Describe the method to obtain salt from sea water. (3 Marks)
Ans: To obtain salt, sea water is collected in shallow pits and left under sunlight. The heat from the sun causes the water to evaporate slowly, turning into water vapour and leaving behind the solid salts. In a few days, when all the water has evaporated, the solid salts remain. Common salt is then separated from other salts and impurities through further purification. This method is simple, uses natural sunlight, and has been practiced traditionally in many coastal regions.

Q14: Explain how churning is used to separate butter from curd, and why the butter floats on top. (3 Marks)
Ans: Churning involves agitating curd with a churner to separate lighter butter from the denser buttermilk. The mechanical action breaks the fat globules in the curd, causing the butter to coalesce and float on top due to its lower density. This method efficiently collects usable butter for consumption, while the remaining liquid can still be used as buttermilk for cooking or drinking.

Q15: Discuss the significance of magnetic separation in recycling waste materials. (3 Marks)
Ans: Magnetic separation is a method that attracts magnetic substances like iron from non-magnetic materials using a magnet. It allows magnetic components to be separated efficiently for recycling and reuse. This process helps reduce environmental pollution, conserves resources, and prevents valuable materials from going to waste. Magnetic separation is therefore an important technique for sustainability and resource management.

Q16: A mixture contains sand, salt, iron filings, and pebbles. Outline a stepwise procedure to separate all components using methods . (4 Marks)
Ans: To separate sand, salt, iron filings, and pebbles: 
(1) Use handpicking or sieving to remove larger pebbles based on size difference; pebbles remain on the sieve while finer mixture passes through. 
(2) Pass a magnet through the remaining mixture for magnetic separation; iron filings stick to the magnet and are collected. 
(3) Dissolve salt from the sand-salt mix in water to form a solution; sand remains insoluble. 
(4) Filter the solution to separate sand as residue; then evaporate the filtrate to recover salt crystals. 

This sequence uses properties like size, magnetism, solubility, and evaporation for complete separation.