Class 6th Ch- Separation of Substances

 

Question 1. What is winnowing? Where is it used?

Answer 1: Winnowing is the process of using wind or air blowing to separate heavier and lighter components of a mixture. Farmers use this method to separate lighter grain husk fragments from heavier grain seeds.

Question 2. How will you separate sand and water from their mixture?

Answer 2: Sand and water will be separated using the decantation and sedimentation methods. First, we leave this mixture for some time. The heavier sand eventually settles to the bottom after some time. The mixture will separate once we pour water into another container.

Question 3. Fill in the blanks:

(a) 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 ____________.

(b) The process of obtaining salt  from sea water is called 

____________ .

(c) When milk, cooled after boiling, is poured onto a piece of cloth, the cream (malai) is left behind. This process of segregating cream from milk is an example of ______. 

(d) The method of separating seeds of paddy from its stalks is called  ____________.

Answer 3: 

(a) sedimentation and decantation

(b) evaporation

(c) filtration

(d) threshing

Question 4. Name the process by which we get salt from ocean water.

Answer 4: Evaporation is the process by which we get salt from ocean water.

Question 5. What is Sieving? Where can it be used?

Answer 5: Fine particles are separated from larger particles during the sieving process using a sieve. It is utilised on building sites or in grain mills. Wheat contaminants like husks and stones are eliminated in the flour mill. Sand is sieved to remove stones and pebbles.

Question 6. A mixture of iron nails, salt, oil and water is provided to you. Give stepwise methods to separate each component from this mixture.

Answer 6: A mixture of iron nails, salt, oil and water can be separated by the following steps:

• Iron nails can be picked out by hand or using a magnet.
• By using a separating funnel or decantation, remove the oil.
• Using evaporation, evaporate the salt and water mixture. Salt is left behind when water is condensed again.

Question 7. What is centrifugation?

Answer 7: Centrifugation is the process of separating a mixture through spinning. Skim milk from whole milk, water from your clothes, and blood cells from your blood plasma are separated using it.

Question 8. Name and describe briefly a method which can help separate a mixture of husk from grains. What is the principle of this method?

Answer 8: Winnowing is a method for removing the husk from grains. The lighter husk gets carried away by air and falls to the earth when the mixture is allowed to fall from a height. This technique is based on the idea that the wind will carry lighter particles away in a mixture of different weighted components.

Question 9. What is a strainer?

Answer 9: A strainer is an object with holes through which a liquid is poured to separate the liquid from any particles.

Question 10. Name the process used to separate cream from curd.

Answer 10: Centrifugation is the process used to separate cream from curd.

Question 11. In the activity, a teacher dissolved a small amount of solid copper sulphate in a tumbler half filled with water. Which method would you use to get back solid copper sulphate from the solution?

(a) Decantation

(b) Evaporation

(c) Sedimentation

(d) Condensation

Answer 11: (b) Evaporation

Explanation: Water evaporates during the evaporation of the copper sulphate solution, leaving solid copper sulphate behind.

Question 12. List some materials that are used as filters.

Answer 12: 

• Cotton
• Filter paper
• Sand
• Charcoal
• Muslin cloth

Question 13. Define the term handpicking.

Answer 13: Handpicking is the method of manually removing slightly larger particles from a mixture. For instance, handpicking can be used to separate stone fragments from grains of rice or wheat.

Question 14. Paheli bought some vegetables such as french beans, lady’s finger, green chillies, brinjals and potatoes, all mixed in a bag.

Which of the following methods of separation would be most appropriate for her to separate them?

(a) Winnowing

(b) Sieving

(c) Threshing

(d) Hand picking

Answer 14: (d) Hand picking

Explanation: Due to their large size, handpicking is the preferred way for separating the vegetables.

Question 15. What is the use of decantation?

Answer 15: Decantation is used to separate insoluble solids or liquids from the liquid. 

Question 16. Elaborate on the process of filtration.

Answer 16: The filtering process involves removing an insoluble material from a liquid using a filtering medium, such as filter paper, cloth, a strainer, etc. The liquid free of suspended debris flows through the filter paper and is collected as filtrate. At the same time, the solid, insoluble substance is held on the filter paper as residue. The steps of evaporation and crystallisation can separate some soluble infiltration components.

Question 17. Four mixtures are given below.

(i) Kidney beans and chickpeas

(ii) Pulses and rice

(iii)  Potato wafers and biscuits

(iv) Rice flakes and corn

Which of the following can be separated by the method of winnowing?

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (i) and (iii)

(d) (iii) and (iv)

Answer 17: (d) (iii) and (iv)

Explanation: Mixtures of rice flakes and corn and potato wafers and biscuits can be separated by winnowing because there is a difference in the weight of the two components, one being lighter and the other being heavier.