NCERT Class 6 Science Chapter 5 Separation of Substances

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NCERT Class 6 Science Chapter 5 Separation of Substances

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Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 6 Science Solutions are part of All Subject Solutions. Here we have given NCERT Class 6 Science Chapter 5 Separation of Substances and Textbook for All Chapters, You can practice these here.

Separation of Substances

Chapter: 5

NCERT TEXT BOOK EXERCISES

Q. 1. Why do we need to separate different components of a mixture? Give two examples.

Ans: Before we use a substance, we need to separate harmful or non-useful substances that may mixed in it. Sometimes, we separate even useful components if we need use them separately.

Examples: (i) Tea leaves are separated from the liquid with a strainer while preparing tea. These tea leaves are non- useful substances in the mixture.

(ii) Milk or curd is churned to separate the butter. Here butter is a useful component which we need to use separately.

Q. 2. What is winnowing? Where is it used? 

Ans: Winnowing is the method of separating husk from grains with the help of wind. This method is commonly used by farmers to separate lighter husk particles from heavier seeds of grain.

Q. 3. How will you separate husk or dirt particles from a given sample of pulses before cooking?

Ans: Husk or dirt particles can be separated by winnowing, being lighter they will fly away from pulses.

Q. 4. What is sieving? Where can it be used ? [Delhi 2014]

Ans: The method used to separate the components of different sizes in a mixture using a sieve is called sieving.

This method is used when one of the components is larger than the holes in the sieve. The smaller components pass through the holes in the sieve while the larger components are left behind.

Q. 5. How will you separate sand and water from their mixture? 

Ans: A mixture of sand and water can be separated by the method of sedimentation and decantation. The mixture of sand and water is first allowed to stand for some time. Since the sand is heavy, it settles down at the bottom of the container. Water forms the upper layer and the sedimented sand is separated by decantation. In decantation, the liquid forming the upper layer is carefully poured out leaving behind the settled sand at the bottom of the container.

Q. 6. Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?

Ans: Sugar can be separated from wheat flour by sieving. Due to difference in the size of particles, sugar will stay on sieve and flour will pass through it.

Q. 7. How would you obtain clear water from a sample of muddy water?

Ans: We will obtain clear water from a sample of muddy water by the process of filtration.

Take a small quantity of muddy water in a beaker. Allow it to stand for some time. 

The particles of sand settle down to the bottom of the beaker. This settling down of heavier particles is called sedimentation. Transfer the clear supernatant water (upper of water) carefully to another beaker. This process of separating liquid without disturbing the solid particles is called decantation.

Q. 8. Fill up the blanks: 

(a) The method of separating seeds of paddy from its stalk is called ___________.

Ans: Winnowing.

(b) When milk is poured onto a piece of cloth the cream (malai) is left behind on it. This process of separating cream from milk is an example of ___________.

Ans: Filtration.

(c) Salt is obtained from sea water by the process of ___________.

Ans: Evaporation.

(d) Impurities settled at the bottom when muddy water was kept over night in a bucket. The clear water was then poured of from the top. The process of separation used in this example is called __________.

Ans: Decantation.

Q. 9. True or False?

(a) A mixture of milk and water can be separated by filtration.

Ans: False.

(b) A mixture of powdered salt and sugar can be separated by the process of winnowing. 

Ans: False.

(c) Separation of sugar from tea can be done with filtration.

Ans: False.

(d) Grain and husk can be separated with the process of decantation.

Ans: True. 

Q. 10. Lemonade is prepared by mixing lemon juice and sugar in water. You wish to add ice to cool it. Should you add ice to the lemonade before or after dissolving sugar? In which case would it be possible to dissolve more sugar?

Ans: We should add ice in lemonade after dissolving sugar in it, because sugar dissolves more before adding ice. It would be possible to dissolve more sugar before adding ice in the lemonade, because it dissolve more into hot than in cold. After mixing ice it gets cool and less sugar will dissolve in it. 

SOME OTHER IMPORTANT QUESTIONS FOR EXAMINATION

VERY SHORT ANSWER QUESTIONS

Q.1. What Substance is used for loading the clay particles suspended in muddy water?

Ans: Alum.

Q.2. Which method is used to separate the comments of a mixture which are of different sizes?

Ans: Sieving.

Q. 3. How will you separate mango from a mixture of mango and apple?

Ans: By hand-picking.

Q. 4. Which method is used to separate grains from stalk? 

Ans: Threshing.

Q. 5.Name the method by which we get salt from ocean water.

Ans: Evaporation.

Q. 6. Which method is used to separate a mixture of tea-leaves and iron filings?

Ans: By magnet.

Q. 7.Name the process by which water is separated from rice and pulses after washing them.

Ans: The water is separated from rice and pulses by decantation.

Q. 8. Name the process of obtaining clear water from muddy water in which alum is used.

Ans: Loading.

Q. 9.Name one method for a mixture of chalk powder and water.

Ans: A mixture of chalk and water is separated by filtration.

Q. 10. Name four materials which can be used as ‘filters’ in the process of filtration.

Ans: A wire-mesh, a piece of cotton, a piece of muslin cloth (fine cloth) and strainer can be used as filters.

Q. 11. What name is given to the solution in which no more substance can be dissolved at that temperature?

Ans: Saturated solution.

Q. 12. What happens when a saturated solution is heated?

Ans: It becomes unsaturated.

Q. 13. What happens when a hot saturated solution is cooled? 

Ans: Crystals will be formed.

Q. 14.What is the effect of temperature on the solubility of solids in liquids?

Ans: The solubility of liquids increases with increase in temperature.

Q. 15. Name the method used in cashewnut factories to separate cashewnuts of different sizes.

Ans: Sieving.

SHORT ANSWER QUESTIONS

Q. 1.Can the constituents of a mixture containing saw dust and water separated by decantation? Give reason.

Ans: The constituents of the mixture containing saw dust and water cannot be separated by decantation because saw dust particles remain suspended in the water and do not settle down to the bottom of the container.

Q. 2 What do you mean by decantation? What are its uses?

Ans: Decantation is a process by which we can remove a liquid without disturbing the solid settled down in the bottom.

Uses: This method can be used to separate a mixture of

(i) sand and water.

(ii) mixture of two liquids which are not miscible-water and oil.

Q. 3. How will you separate a mixture of sulphur in water?

Ans: Take the mixture of water and sulphur in a beaker. Pour the mixture on the filter paper with the help of a glass rod so that the liquid stands below the edge of the cone. The residue that remains on the filter paper is sulphur. Now dry it to get sulphur and water is collected in beaker.

Q. 4. (a) State one use of the method of winnowing. 

(b) Give one use of the ‘hand-picking’ method of separating mixtures in daily life.

Ans: (a) The method of winnowing is used to separate husk from various types of grains like wheat, rice etc.

(b) The method of hand-picking is usually used to separate undesirable substances such as small pieces of stones from wheat, rice and pulses.

Q. 5. Define the term threshing. What is its principle?

Ans: Threshing: Threshing is the process in which stalks (of wheat, paddy, etc.) are beaten to separate grains from the stalks and from the chaff that covers the grains.

The method of separation is based on the fact that the ‘stalks’ (or stems) of the crop plants and the ‘chaff’ are soft materials whereas the grains themselves are very hard. Being soft, stalk and chaff can be broken into pieces on beating but the grains remain unaffected.

Q. 6. The mixture of a powdered white solid P and a liquid Q can be separated by filtration. The solid P is left behind on the filter paper but clear liquid Q passes through the filter paper and collects in the beaker kept below.

(a) Name one solid which could be like P. 

Ans: Chalk-powder.

(b) Name the liquid which Q could be.

Ans: Water

(c) What name is given to the solid left on the filter paper?

Ans: Residue

(d) What name is given to the clear liquid collected in the beaker? 

Ans: Filtrate.

Q. 7. What is a saturated solution? What is the effect of heating on the saturated solution? 

Ans: A solution is said to be saturated when a solvent can dissolve no more of a solute at a particular temperature. If the saturated solution of a substance at a particular temperature is heated to a higher temperature, then the solubility of the substance increases and more of substance can be dissolved in it.

Q. 8. What is meant by condensation? What is the significance of condensation in nature?

Ans: Condensation: The process by which vapour of any liquid is converted into liquid by cooling is called condensation.

Significance: When the clouds enter a colder region, the water vapour gets cooled and forms water droplets. These droplets fall down as rain.

Q. 9. What do you understand by super saturated solution? Give an example.

Ans: A solution is said to be super saturated when it contains more of the solute than could be dissolved by the solvent under normal conditions.

Example: Carbonated water and beer are examples of super saturated solutions.

SHORT ANSWER QUESTIONS

Q. 1. A mixture contains two components A and B. The component A is a white solid which is soluble in water. It is obtained on a large scale from sea-water by the process C. The component B consists of tiny pieces called filings which can be attracted and removed from the mixture by a device D.

(a) What do you think the component A? 

Ans: Common salt.

(b) Name the process ‘C’.

Ans: Evaporation.

(c) Name the component ‘B’

Ans: Iron fillings.

(d) What could the device D be? 

Ans: Magnet.

Q. 2. How will you separate a mixture of sand and salt?

Ans: (i) Some water is added to the mixture of sand and salt in a beaker and stirred. Salt dissolves in water to form salt solution whereas sand remains undissolved. It is then filtered.

(i) On filtering, sand is obtained as a residue on the filter paper and salt solution is obtained as filtrate.

(iii) The salt solution (filtrate) is evaporated when pure salt is left behind.

Q. 3. Which separation techniques will you apply for the separation of the following?

(i) Butter from curd.

(ii) Oil from water.

(iii) Tea leaves from tea.

(iv) Iron pins from sand.

(v) Wheat grains from husk.

(vi) Fine sand particles suspended in water.

Ans: (i) Churning.

(ii) Separating funnel (gravity method)

(iii) Filtration 

(iv) Magnetic separation method

(v) Winnowing

(vi) Loading, sedimentation, filtration

Q. What is strainer? How will you prepare cheese (paneer)?

Ans: Strainer Strainer is a kind of sieve which is used to separate a liquid from solid. For making paneer, a few drops of lemon juice are added to milk as it boils. This gives a mixture of particles of solid paneer and liquid. The paneer is then separated by filtering the mixture though a fine cloth or strainer.

Q. 5. What are the applications of centrifugation? 

Ans: (i) It is used in diagnostic laboratories to test blood and urine.

(ii) It used in dairies and homes to separate butter from cream.

(iii) It is used in washing machines to squeeze out water from wet clothes. 

Q.6. Lemonade is prepared by mixing. sugar and lemon juice in water. You wish to add ice to cool it. Should you add ice to the lemonade before or after dissolving sugar in water? In which case it would be possible to dissolve more sugar?

Ans: We should add ice after dissolving sugar in water. 

(i) Initially, the water is at room temperature so it is warm water. Warm water can dissolve more sugar and that too quite rapidly. 

(ii) If ice is added first, then the water will become cold. Cold water will dissolve less sugar and too quite slowly. 

Q.7. What is winnowing? How is winnowing done?

Ans: Winnowing is the method of separating husk from grains with the help of wind.

The mixture of wheat grains and husk is taken in a winnowing basket. The farmer stands at a higher platform from the ground and allows the mixture of wheat grains and husk to fall down from a height by shaking the winnowing basket continuously. The wheat grains, being heavy, fall down. vertically to the ground and form a heap of wheat grains. The husk particles, being lighter are carried away by wind to a greater distance. So, the husk forms a separate heap at a small distance away from the heap of grains. In that way, husk gets separated from wheat grains.

Q.8. How can we separate cream from milk?

Ans: When milk is rotated at a high speed in a centrifugation machine, the lighter fat particles collide with each other to form cream which stays on the surface while the heavier particles of the milk are forced to come to the bottom. As a result separation occurs and the cream is collected from the outlet provided near the top of the centrifugation machine while the milk is collected through the outlet provided near the bottom of the machine.

Q.9. How you will separate a mixture of common salt, sulphur powder and sand?

Ans: First shake the mixture with carbon disulphide when sulphur powder dissolves leaving being common salt and sand. The mixture is filtered. Evaporation of carbon disulphide from the filtrate gives sulphur powder. The residue left on the filter paper consists of common salt and sand. Shake this mixture well with water when common salt dissolves leaving being sand. The mixture is filtered. Evaporation of from the filtrate gives common salt.

Q.10. Gun powder is a mixture of nitre, sulphur and carbon. How will you separate its constituents?

Ans: Nitre is soluble in water, sulphur is soluble in carbon disulphide while carbon is soluble in neither of the two. Thus, the given mixture is first stirred with water and then filtered. Nitre dissolves while sulphur and carbon remain on the filter paper as residue. Evaporation of water from the filtrate gives nitre.

residue consisting of sulphur and carbon is shaken with carbon disulphide and filtered. Sulphur dissolves while carbon remains on the filter paper as residue. Evaporation of carbon disulphide from the filtrate gives sulphur.

LONG ANSWER QUESTIONS

Q. 1.How will you separate a mixture of iron fillings, common salt, sand and sulphur?

Ans: Iron fillings are separated from the mixture by using a magnet. The remaining mixture of salt, sand and sulphur is stirred with water when salt is dissolved in it. On filtration salt solution is obtained as a filtrate and the residue contains sand and sulphur.

Sand and sulphur mixture is shaken with carbon disulphide, when sulphur dissolves in it but sand remains undissolved. On filtration, sand is obtained as residue and sulphur as filtrate. On evaporating the filtrate carbon disulphide is removed and sulphur is obtained.

Q. 2. How you will purify common salt obtained from sea water?

Ans: The lumps of impure common salt obtained from sea water, are crushed to get powdered salt.

The powdered common salt is dissolved in water to prepare a solution. The solution of common salt is filtered to remove insoluble impurities.

The clear solution of common salt is evaporated by heating to remove some of the water to obtain a concentrated solution. The hot concentrated solution of common salt is allowed to cool. On cooling, the hot solution crystallizes and crystals of pure common salt are obtained.

Q. 3. How will you separate a mixture of iron fillings, chalk powder and common salt?

Ans: (i) Bring a magnet near the mixture several times. All the iron fillings will stick to the magnet and get separated. We are then left with a mixture of chalk powder and common salt.

(ii) Some water is added to the mixture of common salt and chalk powder and stirred. Common salt dissolves in water to form salt solution, whereas chalk powder remains undissolved.

(iii) On filtering, chalk powder is obtained as a residue on the filter paper and salt solution is obtained as filtrate.

(iv) The salt solution (filtrate) is evaporated when pure common salt is left behind. The mixture has been separated by using three methods of separation magnetic separation, filtration and evaporation.

HIGHER ORDER THINKING SKILL QUESTIONS

Q. 1. There are four mixtures A, B, C and D. The mixture A contains sand and sugar, mixture B contains chalk powder salt, mixture C contains salt and s sugar, whereas mixtures D contains sugar and charcoal powder. Which one of these mixtures cannot be separated by using water as solvent ? Why?

Ans: Mixture C containing salt and sugar cannot be separated by using water as solvent because both, salt as well as sugar are soluble in water.

Q. 2. Component A dissolves in component B to form a liquid mixture. If this mixture is subjected to a process C, then only component A can be recovered. But if the mixture is subjected to another process D, then both the components A and B can be recovered from their mixture.

(a) Name one component which could be like A

Ans: Common salt.

(b) Give one example of a component like B.

Ans: Water.

(c) Name the process C.

Ans: Evaporation.

(d) What could process D be?

Ans: Distillation.

Q. 3. How would you obtain a sample of sulphur from a mixture of sulphur and carbon?

Ans: Shake the mixture of sulphur and carbon with carbon disulphide and filter. Sulphur will be present in the filtrate and residue carbon. The filtrate is evaporated when carbon disulphide vaporises while sulphur is left behind.

Q. 4. The sample of water collected from a shallow pond has some tiny particles A suspended in it. When a piece of substance B tied to a thread is rotated in this sample of water kept in a beaker, then the suspended particles settle down at the bottom of the beaker quite rapidly. The process is called C. The clear water is then separated from the settled particles by the technique D.

(a) What could the particle A be?

Ans: Clay particles.

(b) Name the substance B.

Ans: Alum.

(c) What is the name of process D?

Ans: Loading

(d) Name the technique D.

Ans: Decantation 

Q.5. Why do doctors often instruct us to shake the bottle containing liquid medicine before use?

Ans: It is because some solid particles in these liquid medicines settle down at the bottom of the bottle.

SKILL BASED QUESTIONS

Q.1. Observe the following diagram and answer the questions given below: 

(a) Suggest a caption / title to the process shown in figure. 

(b) What method is used in this process?

Ans: (i) Separation of tea leaves with a strainer.

(ii) Filtration.

Q. 2. The following diagram shows the method used in taking out butter from milk and curd. Answer the questions after observing the diagram carefully.

(i) What is the name of this process? 

(ii) Explain the process / principle. 

Ans: (i) Churning.

(ii) Churning involves rotation of milk/ curd at a high speed. Cream being lighter collects towards the centre. The cream floating on the surface of defatted milk can be separated by sieving.

Q. 1. Fill in the following blanks with suitable words:

(i) Insects can be separated from wheat by ___________.

Ans: Hand-picking.

(ii) The process heating a liquid to form vapour and then cooling the vapour to get back liquid is called ___________.

Ans: Distillation.

(iii) Cream is separated from milk by ___________.

Ans: Churning.

(iv) Common salt is obtained from sea water by ___________.

Ans: Evaporation.

(v) Husk is separated from rice by ___________.

Ans: Winnowing.

(vi) The changing of a liquid into vapours (or gas) is called ___________.

Ans: evaporation

(vii) method used to separate the components of different sizes in a mixture using a sieve is called ___________.

Ans: sieving

(vi) Sedimentation can be made quicker by adding ___________ into it. 

Ans: Alum

(ix) Pebbles are separated from grains by ___________.

Ans: Hand-picking.

(x) A mixture of tea-leaves and iron fillings can be separated by ___________.

Ans: magnet.

Q. 2. State whether the following statements are true or false: 

(i) The process of winnowing is used to remove small stone particles from wheat.

Ans: False.

(ii) Cream is separated from milk by sieving.

Ans: False

(iii) Common salt is separated from the solution in water by decantation.

Ans: False

(iv) Filtration cannot remove any solid substances which are dissolved in a liquid. 

Ans: True.

(v) Churning is used for obtaining butter from curd.

Ans: True.

(vi) A salt from its solution in water can be recovered by evaporation.

Ans: True.

(vii) Wood is a magnetic substance.

Ans: False.

(viii) Salt cannot be obtained from sea water by evaporation method.

Ans: False.

(ix) Two liquids that do not mix with each other can be separated by decantation.

Ans: True.

(x) When rice and pulses are washed with water before cooking then the water is separated from them by the process of decantation.

Ans: True. 

Q.3. Match the column:

 Ans: 

Q. 4. Write one word for the following: 

(i) Separation of fine particles of insoluble solid a liquid.

Ans: Filtration.

(ii) The process by which vapour of any liquid is converted into liquid by cooling.

Ans: Condensation.

(iii) Method to obtain common salt from sea water. 

Ans: Evaporation.

(iv) The maximum mass (in grams) of solute that can be dissolved in 100 g of the solvent.

Ans: Solubility.

(v) A solution in which no more solute can be dissolved.

Ans: Saturate solution.

(vi) The process of beating out the grains from the harvested crop.

Ans: Threshing.

(vii) The process of pouring out the clear upper liquid without disturbing the sediments. 

Ans: Decantation.

(viii) The process used to separate mixture containing components of different size, shape and colour.

Ans: Sieving.

(ix) A homogeneous mixture of solute and solvent. 

Ans: Solution.

(x) The process of removing unwanted components such as pebbles, straw from rice and pulses by hand.

Ans: Hand-picking.

MULTIPLE CHOICE QUESTIONS

(i) The method of separation used to separate stones from rice is:

(a) Hand picking.

(b) Threshing.

(b) Winnowing. 

(d) Any of the above. 

Ans: (a) Hand picking.

(ii) The separation of grains from husk is done by the process of:

(a) Hand picking.

(b) Sieving.

(c) Winnowing.

(d) Threshing.

Ans: (c) Winnowing.

(iii) A solid is dissolved in water. Which one of the following methods can be used to separate it?

(a) Filtration.

(b) Evaporation.

(c) Sublimation.

(d) Decantation.

Ans: (b) Evaporation.

(iv) Common salt is recovered from sea water by the process of:

(a) Filtration.

(b) Distillation.

(c) Condensation.

(d) Evaporation.

Ans: (b) Evaporation.

(v) When rice and pulses are washed with water before cooking then the water separated from them by the process of:

(a) Filtration.

(d) Evaporation.

(b) Decantation.

(c) Distillation.

Ans: (b) Decantation.

(vi) Tincture of iodine is a weak solution of iodine in alcohol. Iodine can be recovered from tincture of iodine by the process of:

(a) Filtration.

(b) Distillation.

(c) Evaporation.

(d) Decantation.

Ans: (c) Evaporation.

(vii) At water treatment plants which supply drinking water, the river water is filtered by using:

(a) Filter papers.

(b) Porcelain filters.

(c) Cloth filters.

(d) Sand filters.

Ans: (d) Sand ‘filters.

(viii) Which of the following mixtures cannot be separated by using water as solvent followed by filtration and evaporation?

(a) Sand and sugar.

(b) Salt and chalk powder.

(c) Sand and Sulphur.

(d) Blue vitriol and sand.

Ans: (c) Sand and Sulphur.

VALUE BASED QUESTIONS

Q. 1. Arun’s sister added some water into the bottle containing olive oil and she was afraid of the scolding. Arun helped his sister and separated the water from olive using bottle as separating funnel.

(a) What is the principle of using and working of separating funnel?

Ans: The principle of separating funnel is difference in the densities of two liquids.

(b) Suggest two separation techniques used to separate liquid mixtures.

Ans: Liquid mixtures can be separated by filtration, distillation and fractional distillation.

(c) What value of is seen in the above case? 

Ans: Arun showed the value of helping, caring and responsible Behaviour. 

Q. 2. During rainy season, the river water becomes muddy. It cannot be made fit for drinking purposes just by decantation or filtration.

(i) Mohan asked his teacher, what makes water muddy?

Ans: The presence of clay particles makes water muddy.

(ii) Why can’t muddy water be purified by either decantation. 

Ans: The clay particles carry the same negative charge which repel each other and hence they do not settle at the bottom of the container. Therefore, decantation cannot be used to purify muddy water Further, clay particles are much smaller in size than the size of the pores in the filter paper. As a result, they easily pass through the pores of the filter paper and hence muddy water cannot be made fit for drinking by filtration.

(iii) Tell a method to make muddy water fit for drinking purposes.

Ans: When alum is added to muddy water, the positively charged aluminium ions of the alum neutralize the negative charge of clay particles. The neutral clay particles then combine together to form bigger particles which ultimately settle down at the bottom of the container.The pure water can then be obtained by decantation or filtration.

(iv) What value of teacher is seen in the above case?

Ans: Teacher is an aware citizen, environmentally concerned and with scientific attitude.