Separation of Substances | Science 6th | Chapter 5 | Questions and Answers

JANDKNCERT | Science 6^th |

Separation of Substances | Science 6th | Chapter 5 | Questions and Answers

 

Chapter 5: Separation of Substances

 

Introduction

In Chapter 4, we learnt about Sorting Materials into Groups in which we learnt about the objects around us, lustre, size and properties of objects, such as, hardness, appearance, solubility, and transparency. We learnt to sort the materials in different groups, on the basis, of their properties.

In this chapter, you will learn about the Separation of Substances. The following points will help you to understand this chapter easily.

•     Handpicking, winnowing, sieving, sedimentation, decantation and filtration are some of the methods of separating substances from their mixtures.

•     Husk and stones could be separated from grains by handpicking.

•     The husk is separated from heavier seeds of grain by winnowing.

•     The difference in the size of particles in a mixture is utilised to separate them by the process of sieving and filtration.

•     In a mixture of sand and water, the heavier sand particles settle down at the bottom and the water can be separated by decantation.

•     Filtration can be used to separate components of a mixture of an insoluble solid and a liquid.

•     Evaporation is the process in which a liquid gets converted into its vapour. Evaporation can be used to separate a solid dissolved in a liquid.

•     A saturated solution is one in which no more of that substance can be dissolved.

•     More of a substance can be dissolved in a solution by heating it.

•     Water dissolves different amounts of soluble substances in it.

 

Let us try to answer some questions taken from the NCERT Book of Science Class 6th. This Exercise is taken from the same book.

 

Exercises

Q1. Why do we need to separate different components of a mixture? Give two examples.

 

Answer.

We need to separate different components of a mixture because this helps us to use only useful components and keeps us away from harmful components. For example, we separate stones from rice before cooking, and we separate tea leaves from the tea before drinking.

 

Q2. What is winnowing? Where is it used?

 

Answer.

The method of separating non-useful components from a mixture by blowing air or wind is known as winnowing. This method is commonly used by farmers to separate lighter husk particles from heavier seeds of grain.

 

Q3. How will you separate husk or dirt particles from a given sample of pulses before cooking?

 

Answer.

We can use, handpicking method or take the mixture in a plate and tilt the plate at some height on a clean plate; this will remove the non-useful components from the sample of pulses. We can use other methods also at our home to separate harmful components from this mixture.

 

Q4. What is sieving? Where is it used?

 

Answer.

The method by which the smallest particles or impurity is separated or filtered using a sieve is known as sieving. It is commonly used in kitchens where impurities in flour are removed before making bread, and it is also used to separate impurities from the sand on construction sites.

 

Q5. How will you separate sand and water from their mixture?

 

Answer.

We can separate sand and water mixture with the help of the sedimentation method. Put the mixture in a tumbler. Wait for some time, till the sand is settled down at the bottom of the tumbler. Now carefully remove the water and let the sand settle at the bottom.

 

Q6. Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?

 

Answer.

Sugar mixed with wheat flour can be separated by using the sieving method. Put the mixture on the sieve and sway it left to right and right to left, till the flour is passed through the holes of the sieve and the sugar particles remain in the sieve. Sugar particles are bigger and cannot pass through the small holes of the sieve.

 

Q7. How would you obtain clear water from a sample of muddy water?

 

Answer.

We can obtain clear water from a sample of muddy water by using two methods, that is, sedimentation and filtration. Take the sample of muddy water in a glass. Let it stand for some time till the impurity settles at its bottom. Now slightly tilt the glass without disturbing the water and let the clear water flow in another glass. If water still has dust in it, then filter the water using filter paper. This will help us to obtain clear water from a sample of muddy water.

 

Q8. Fill up the blanks

a. The method of separating seeds of paddy from its stalks is called __________.

b. When milk, cooled after boiling, 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 ___________.

c. Salt is obtained from seawater by the process of ___________.

d. 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 ___________.

 

Answer.

a. The method of separating seeds of paddy from its stalks is called threshing.

b. When milk, cooled after boiling, 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 filtration.

c. Salt is obtained from seawater by the process of evaporation.

d. 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 sedimentation.

 

Q9. True or false:

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

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

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

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

 

Q10. 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?

 

Answer.

We should add ice to the lemonade after dissolving sugar. It is possible to dissolve more sugar before cooling the solution because sugar settles at the bottom after cooling. Heating allows more sugar to dissolve after saturation.

 

Q11. Mustard oil gets accidentally mixed with water. How will you remove mustard oil from the water?

 

Answer.

Mustard oil can be removed from the water by using the decantation method. Oil is not miscible with water it is lighter than water and keeps floating on the water as a separate layer.

 

Q12. A tiny iron drill of a carpenter falls into a heap of straw. Suggest a convenient way of recovering the drill?

 

Answer.

We know that the drill is made of metallic material therefore we can use large magnets to recover the drill from the heap of straw. Handpicking method can also be used to recover the iron drill from a heap of straw.

 

Q13. Differentiate between a saturated solution and an unsaturated solution?

 

Answer.

A solution is said to be saturated if it cannot dissolve more solute in it while a solution is unsaturated if it allows dissolving more solute in it.