Living Science Solutions for Class 6 Science Chapter 5 Separation Of Substances are provided here with simple step-by-step explanations. These solutions for Separation Of Substances are extremely popular among class 6 students for Science Separation Of Substances Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Living Science Book of class 6 Science Chapter 5 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Living Science Solutions. All Living Science Solutions for class 6 Science are prepared by experts and are 100% accurate.

Page No 55:

Question 1:

Most of the substances we see around us are
(a) pure elements.
(b) pure compounds.
(c) impure elements.
(d) mixtures.

Answer:

(d) mixtures

Most of the substances we see around us are mixtures of different elements and compounds.

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Question 2:

A solution of salt in water is a
(a) compound.
(b) homogeneous mixture.
(c) heterogeneous mixture.
(d) element.

Answer:

(b) homogeneous mixture

When salt is dissolved in water, the salt is distributed uniformly in the solution. Thus, the salt solution is a homogeneous mixture.

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Question 3:

The property used in separating a mixture of two solids by winnowing is
(a) difference in colour.
(b) difference in size.
(c) difference in weight.
(d) attraction by magnet.

Answer:

(c) difference in weight

Winnowing is used to separate two solids of different weights, such as wheat and chaff.

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Question 4:

The process of settling down of particles of a solid in a liquid is
(a) decantation.
(b) sublimation.
(c) sedimentation.
(d) filtration.

Answer:

(c) sedimentation

The process of settling down of particles of a solid in a liquid is known as sedimentation.

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Question 5:

Which method is used to obtain a pure liquid from a solution?
(a) distillation
(b) condensation
(c) filtration
(d) loading

Answer:

(a) distillation

Distillation can be used to obtain a pure liquid from a solution.



Page No 56:

Question 6:

The temperature of a saturated solution of sugar in water is raised by 10 °C. Which of these statements is now true?
(a) It will continue to be saturated.
(b) It will become unsaturated.
(c) Whether it remains saturated or becomes unsaturated depends on the amount of water taken.
(d) It will continue to be saturated, but if the temperature is increased beyond 10 °C it will become unsaturated.

Answer:

(b) it will become unsaturated

If the temperature of saturated sugar solution is increased by 10 oC, then more sugar can be dissolved in the solution and the solution becomes unsaturated.

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Question 7:

Which of the following can dissolve in water?
(a) only solids
(b) only solids and liquids
(c) solids, liquids and gases
(d) only liquids

Answer:

(c) solids, liquids and gases

Solids such as salt, liquids such as alcohol and gases such as nitrogen and oxygen can dissolve in water.

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Question 8:

Sedimentation and decantation are useful to separate
(a) immiscible liquids.
(b) soluble solid from liquid.
(c) insoluble solid from liquid.
(d) insoluble solid from a liquid where the solid is heavier than the liquid.

Answer:

(d) insoluble solid from a liquid where the solid is heavier than the liquid

Decantation and sedimentation can be used to separate solids from a liquid when the solid is heavier than the liquid and is insoluble in the liquid.

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Question 9:

A commonly used chemical for loading is
(a) hydrogen.
(b) alum.
(c) sulphur.
(d) common salt.

Answer:

(b) alum

Alum is a commonly used chemical for loading to speed up sedimentation.

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Question 10:

To get only the pure solid from its solution in water, which method will you use?
(a) evaporation
(b) distillation
(c) filtraction
(d) none of these

Answer:

(a) evaporation

Evaporation is the process used to get a pure solid from its solution in water.

Page No 56:

Question 1:

There are very few pure elements or compounds around us. Most substances are mixtures. True or false?

Answer:

True, most of the substances around us exist in the mixed state and not as pure elements or compounds.

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Question 2:

The constituents of all mixtures are uniformly spread throughout the mixtures. True or false?

Answer:

False, the constituents of a heterogeneous mixture are not uniformly spread throughout the mixture.

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Question 3:

Is a solution of sugar in water homogeneous or heterogeneous?

Answer:

In case of a sugar solution, the sugar is distributed uniformly in the water. Thus, sugar solution is a homogeneous solution.

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Question 4:

Name one property of a compound that remains fixed and can be used to test if the compounds has impurities in it.

Answer:

The melting point and boiling point are two properties of a compound that can be used to test its purity as they remain fixed.

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Question 5:

We have to separate a mixture into its constituents because only pure compounds are useful to us. Mixtures are not of much use. True of false?

Answer:

False, mixtures are also very useful to us. For example, the air we breathe is also a mixture of gases.

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Question 6:

Can a mixture of sawdust and water be separated by sedimentation and decantation?

Answer:

Sedimentation and decantation cannot be used to separate sawdust from water because sawdust is not heavier than water. Sedimentation and decantation can only be used to separate an insoluble solid from a liquid if the solid is heavier than the liquid.

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Question 7:

Which method gives a better separation of an insoluble solid from a liquid−sedimentation and decantation, or filtration?

Answer:

An insoluble solid can be separated from a liquid more efficiently by filtration. Filtration can separate out solids that are also lighter than the liquid and it is faster since, liquid need not be left to stand.

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Question 8:

Name the method which is used to speed up sedimentation.

Answer:

The method used to speed up sedimentation is known as loading.

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Question 9:

Which separation method is used to separate wheat grains from chaff?

Answer:

Wheat grains are separated from chaff using the process of winnowing.

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Question 10:

Name the method used to obtain salt from sea water.

Answer:

Salt is obtained from sea water by evaporation of sea water.

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Question 11:

Which method will you use to get a pure liquid from a solution containing several soluble solids in the liquid?

Answer:

Distillation can be used to get a pure liquid from a solution containing several soluble solids in the liquid.

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Question 12:

Which apparatus is used to cool the liquid vapours during distillation?

Answer:

A Liebig's condensor is used to cool liquid vapours during distillation.

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Question 13:

Which apparatus is used to separate two immiscible liquids?

Answer:

Two immiscible liquids can be separated using a separating funnel.

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Question 14:

Solubility of most solids in water increases with rise in temperature. True or false?

Answer:

True. The solubility of most solids in water increases with rise in temperature.



Page No 57:

Question 1:

You are given a sample of water. How will you find out whether it is pure or not?

Answer:

To find out if water is pure or not, we can measure the boiling point of the sample. If the sample boils at 100 oC, then the water is pure.

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Question 2:

What is the principle used in the separation of mixtures?

Answer:

The principle used in the separation of a mixture employs a special property of one of the components of the mixture. For example, iron pieces mixed with sand can be separated using a magnet as iron gets attracted towards the magnet.

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Question 3:

To use a sieve to separate sand and rice seeds, what should be the size of the holes of the sieve in comparison to the size of sand particles and rice seeds?

Answer:

To separate sand from rice seeds, the holes in the sieve must be larger than the sand particles and smaller than the rice seeds so that, sand particles can easily pass through the sieves leaving behind the rice seeds.

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Question 4:

Which property of a filter paper is used to separate an insoluble solid from a liquid?

Answer:

An insoluble solid can be separated from a liquid using a filter paper as the filter paper allows the liquid to pass through it while the solid will not pass through the filter paper.

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Question 5:

We always talk about a saturated solution at a certain temperature? Why is the temperature specified?

Answer:

The solubility of a solid in a solution increases with increasing temperature. If the temperature of a saturated solution is increased, the solution will become unsaturated. Thus, the temperature plays an important role in specifying whether a solution is saturated or not.

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Question 6:

Under which condition can handpicking be used to separate the constituents of mixture?

Answer:

Handpicking can be used to separate the constituents of a mixture only when the constituents of the mixture are easily visible and can be separated. For example, stones can be separated from rice by handpicking.

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Question 7:

Why are objects at a distance seen more clearly after rain?

Answer:

When it rains, the dust particles in the air get wet and settle down on the ground. As a result, the air is clearer after it rains and objects at a distance are seen more clearly.

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Question 8:

The process of adding alum to water to hasten sedimentation is called 'loading'. Why has this name been given to the process?

Answer:

When alum is added to water, it dissolves in water and makes the suspended impurities heavier making them settle down quickly. Therefore, the addition of alum is known as loading.

Page No 57:

Question 1:

What is the difference between homogeneous and heterogeneous mixtures? Give an example of each mixture.

Answer:

Homogeneous mixture Heterogeneous mixture
The components of the mixture are uniformly distributed in the mixture. The components of a mixture are not uniformly distributed in the mixture.
Example: Salt dissolved in water is a homogeneous mixture. Example: Iron filings mixed in sand is a heterogeneous mixture.

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Question 2:

List three properties of mixtures.

Answer:

Following are the properties of mixtures:

  1. The constituents of a mixture may be present in any ratio.
  2. The constituents of a mixture retain their individual properties The molecules of the constituents do not change. For example, when iron and sulphur are mixed together, their properties do not change.
  3. Constituents of a mixture can be separated easily. For example, stones in rice can be separated easily by visual observation.

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Question 3:

Give two situations where it is necessary to separate a mixture into its constituents.

Answer:

It is necessary to separate a mixture into its constituents for the following situations:

  1. Removing undesirable constituents: For example, it is desirable to remove small stones in rice, or separating tea leaves from tea.
  2. To obtain useful substances: Butter is obtained by churning curds. In the same way, crude oil can be separated into various oils such as petrol, kerosene, diesel etc.

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Question 4:

Draw a labelled diagram to show the arrangement used to filter a mixture of a liquid and an insoluble solid.

Answer:

The arrangement used to filter a mixture of a liquid from an insoluble solid is shown below:

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Question 5:

Draw a labelled diagram of the apparatus used to distil out pure water from a solution.

Answer:



Diagram of apparatus used to distil out pure waterfrom a solution

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Question 6:

How will you separate a mixture of grass, pebbles and sand?

Answer:

To separate a mixture of grass, pebbles and sand, the first step is to pass the mixture through a fine filter. Sand will pass through the filter leaving grass and the pebbles on the filter.
Then, we can winnow the grass and the pebbles since, they have different weights to separate them from each other.

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Question 7:

Explain with the help of a diagram how can a mixture of oil and water be separated.

Answer:

 Oil and water can be separated using a separation funnel. The experimental set up is shown in the figure:



The mixture of oil and water is poured into the separating funnel and allowed to stand for some time. The oil accumulates at the top of the funnel and water near the bottom as shown in the figure. If the stop cock at the bottom is opened, water flows out of the funnel and can be collected in a beaker. If the stop cock is closed when the oil reaches the level of the stop cock, we will have oil in the funnel and water in the beaker.

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Question 8:

Why is water considered as an important solvent?

Answer:

Water is considered an important solvent because:

  1. Water can dissolve a large number of substances that are important for life.
  2. Waste products are also dissolved in water before they can be excreted from the body.
  3. Most of the chemical reactions occurring in the body take place in the presence of water.
  4. Gases such as oxygen and carbon dioxide are soluble in water. This makes aquatic life possible.

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Question 15:

Can water dissolve liquids and gases also?

Answer:

Yes, water can dissolve liquids such as alcohol or milk. It can also dissolve gases such as oxygen, nitrogen etc.

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Question 16:

The solubility of common salt increases rapidly with rise in temperature. True or false?

Answer:

True. The solubility of common salt increases rapidly with rise in temperature.

Page No 57:

Question 1:

A bottle contains either salt or chalk. How will you find out what it has, without tasting it?

Answer:

Salt is soluble in water but chalk is not. So, if you add salt to water it will dissolve and form a clear liquid. However, chalk will not dissolve in water and the chalk dust remains in the water.

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Question 2:

Think and write how you will separate a mixture of water, sand, salt and iron filings. You may have to use a method not given in the chapter to separate sand and iron filings. Think−which property of iron can be used for this?

Answer:

To separate the constituents of the mixture we can use the following steps:

  1. The first step is to pass the mixture through a filter paper. This will separate out a mixture of sand and iron filings from the salt solution.
  2. Now, pass a magnet over the mixture of sand and iron filings. The iron filings will be attracted to the magnet.
  3. Finally, evaporate the salt solution and collect the vapours. Condense the vapour to get water, while salt will be left behind.

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Question 3:

A mixture of salt and sugar is prepared by grinding them together. Do the molecules of the salt and sugar undergo any change?

Answer:

No, the molecules of salt and sugar remain as they are even when salt and sugar are crushed to make a mixture.

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Question 4:

A saturated solution of sugar in water is prepared. The temperature of water is lowered by 5 °C. Will the solution continue to be saturated? Give reasons.

Answer:

If a solution is saturated, it means that more solid will not dissolve in the solution at that temperature. If the temperature is lowered, then the solubility of sugar will be reduced even further and the solution will continue to remain saturated.

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Question 5:

Sea water has salt dissolved in it. You know that pure water can be obtained from sea water by distillation. However, this method is not used to get drinking water from sea water. What do you think is teh reason?

Answer:

Sea water has salt dissolved in it and pure water can be obtained by distillation. However, the energy required to heat large quantities of sea water to make this process widely applicable is too expensive. Also, the condensers required are very expensive if they are to be sized large enough to distill vast quantities of sea water. As a result, distillation is not used to get drinking water from sea water.



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