Class 6 Science Chapter 3 Practice Question Answers - Separation of Substances

Q1: What is the use of decantation?
Ans: Decantation is used to separate insoluble solids or liquids from the liquid.

Q2: Elaborate on the process of filtration.
Ans: 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.

Q3: Define the term handpicking.
Ans: 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.

Q4: 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
Ans: (d)
Due to their large size, handpicking is the preferred way for separating the vegetables.

Q5: 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
Ans: (b)
Water evaporates during the evaporation of the copper sulphate solution, leaving solid copper sulphate behind.

Q6: List some materials that are used as filters.
Ans:

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

Q7: Name and describe briefly a method which can help separate a mixture of husk from grains. What is the principle of this method?
Ans: 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.

Q8: What is a strainer?
Ans: A strainer is an object with holes through which a liquid is poured to separate the liquid from any particles.

Q9: Name the process used to separate cream from curd.
Ans: Centrifugation is the process used to separate cream from curd.

Q10: What is Sieving? Where can it be used?
Ans: 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.

Q11: A mixture of iron nails, salt, oil and water is provided to you. Give stepwise methods to separate each component from this mixture.
Ans: 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.

Q12: What is centrifugation?
Ans: 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.

Q13: Name the process by which we get salt from ocean water.
Ans: Evaporation is the process by which we get salt from ocean water.

Q14: What is winnowing? Where is it used?
Ans: 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.

Q15: How will you separate sand and water from their mixture?
Ans: 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.