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Page No 70:

Question 1:

While making tea, why do we sometimes stir the tea with a spoon?
(a) to mix the ingredients properly
(b) to cool the tea
(c) to dissolve the tea leaves faster
(d) to dissolve the sugar faster

Answer:

(a) to mix the ingredients properly
Stirring mixes the contents of tea properly.

Page No 70:

Question 2:

Which of the following mixtures can be separated by filtration?
(a) a mixture of sand and chalk powder
(b) a mixture of chilli powder and water
(c) a mixture of salt and pepper
(d) a solution of glucose and water

Answer:

(b) a mixture of chilli powder and water
Chilli powder is insoluble in water and can be separated through filtration.

Page No 70:

Question 3:

Which one of the following is a correct statement?
(a) The amount of a solid that dissolves in water increases with a rise in temperature.
(b) The amount of a solid that dissolves in water at different temperatures is the same.
(c) The amount of different solutes that dissolve in water is always the same.
(d) The amount of a solute that dissolves in water decreases with a rise in temperature.

Answer:

(a) The amount of a solid that dissolves in water increases with a rise in temperature.
Solubility increases with increase in temperature.

Page No 70:

Question 4:

Which of the following statements is false?
(a) Tea can be separated from the leaves by filtration.
(b) A mixture of salt and sand can be separated by distillation.
(c) Winnowing will separate wheat grains from husk and dust.
(d) A mixture of sand and salt is partially soluble in water.

Answer:

(b) A mixture of salt and sand can be separated by distillation
The mixture can be separated by filtration, by dissolving the mixture in water. Salt will dissolve in the water, whereas sand will not.

Page No 70:

Question 5:

Which set of three are all mixtures?
(a) milk, soft drink, a teaspoon of sugar
(b) sugar, salt sea water
(c) alloy, salt, lemonade
(d) sea water, milk, crude oil

Answer:

(d) sea water, milk, crude oil
All three are mixtures of various substances. For example, here crude oil is mixture of hydrocarbons.

Page No 70:

Question 6:

Match the items in Column I to those in Column II and say which of the given answers is correct.

Column I Column II
A. loading i. separating
solute from solution
B. decantation ii. separating by
pouring off the top liquid
C. sedimentation iii. weighing down of
solid particles by adding alum
D. distillation iv. settling of solid at
bottom of container


(a) A- iii; B- ii; C-iv; D-i
(b) A- ii; B- iii; C- iv; D-i
(c) A- iii; B-ii; C-i; D-iv
(d) A- iv, B-i; C-iii; D-ii

Answer:

(a) A- iii; B- ii; C-iv; D-i
Loading is the weighing down of solid particles by adding alum, decantation is the pouring off the top liquid, sedimentation is the process in which a solid settles at the bottom of a container and distillation is the process in which a soluble solute is separated from a solution.

Page No 70:

Question 7:

Which of these statements about mixtures is incorrect?
(a) Mixtures contain more than one type of substance.
(b) Smog, alloy and salt water are examples of mixtures.
(c) Heterogeneous mixtures have the components evenly distributed.
(d) A mixture will have the properties of the substances of which it is made.

Answer:

c) Heterogeneous mixtures have the components evenly distributed
The statement given above is wrong, corrected statement would be 'Homogeneous mixtures have the components evenly distributed'.



Page No 71:

Question 8:

_____________ : solvent as sugar: water

(a) solute
(b) solution
(c) saturated solution
(d) distillation

Answer:

(a) solute
Sugar is a solute and water is the solvent.

Page No 71:

Question 9:

Ramlal adds alum to the water stored in his house. How does this help?
(a) Alum dissolves the impurities in water.
(b) Alum causes the impurities to stick to it and settle down.
(c) Alum makes the impurities lighter so that they can float on water and can then be removed easily.
(d) On adding alum, the impurities become harmless.

Answer:

(b) Alum causes the impurities to stick to it and settle down
The impurities stick to alum because of which they become heavier and settle down.

Page No 71:

Question 10:

Air is a
(a) pure substance.
(b) a heterogeneous mixture.
(c) a homogeneous mixture.
(d) none of the above.

Answer:

(c) a homogeneous mixture
Air has a constant ratio of all gases, and is therefore, a homogeneous mixture.

Page No 71:

Question 11:

Match the items in column I to corresponding terms in column II.

Column I Column II
(a) to remove unwanted particles
from rice or dal
(i) sublimation
(b) a liquid in which
solute is dissolved
(ii) separating
funnel
(c) separating by pouring
of top liquid
(iii) solvent
(d) to remove insoluble
solid like cream from milk
(iv) decantation
(e) to separate immiscible
liquids
(v) purify
(f) substance left behind
on the filter paper
(vi) residue
(g) to separate solids
on the basis of variable sizes
(vii) centrifugation
  (viii) hand picking
  (ix) sieving

Answer:

Column I  
Column II
(a) to remove unwanted particles
    from rice or dal
 (viii) hand picking
(b) a liquid in which
     solute is dissolved
(iii) solvent
(c) separating by pouring
     of top liquid
(iv) decantation
(d) to remove insoluble
    solid like cream from milk
(vii) centrifugation
(e) to separate immiscible
     liquids
(ii) separating
      funnel
(f) substance left behind
    on the filter paper
(vi) residue
(g) to separate solids
    on the basis of variable sizes
(ix) sieving

Page No 71:

Question 12:

Name the process you would use for the following.
(a) purification of sea water
(b) separation of a mixture of water and oil
(c) separation of sand and salt
(d) separation of butter from milk
Draw the apparatus you would use for b. and c.

Answer:

(a) purification of sea water: Distillation
(b) separation of a mixture of water and oil: Separating funnel

(c) separation of sand and salt: Filtration
(d) separation of butter from milk: Filtration

Page No 71:

Question 13:

Copy out the following table and write an example of a mixture in each empty box.
For example. coffee is a mixture of a solid and a liquid.

  Solid Liquid Gas
solid   coffee  
liquid      
gas      

Answer:

  Solid Liquid Gas
solid alloy coffee smog
liquid tea crude oil water
gas dust storm aerated drink air

Page No 71:

Question 14:

Mention the property on which the separation of the following mixtures would be based:
(a) mixture of husk and wheat
(b) mixture of vinegar and oil
(c) mixture of flour and raisins

Answer:

(a) mixture of husk and wheat: Weight
(b) mixture of vinegar and oil: Density
(c) mixture of flour and raisins: Size

Page No 71:

Question 15:

Define:
(a) a pure substance
(b) sublimation
(c) loading
(d) separation of mixture

Answer:

(a) A substance which if free form any impurity i.e., a substance which is made up of only one      kind of substance, is called pure.
(b) Sublimation is the process of transition of solid directly into gas.
(c) Loading is the process of sticking light particles like mud onto heavy particles like alum,      so that they become heavy and settle down at the bottom.
(d) The segregation of different components of mixtures depending upon their physical                  properties is called separation of mixtures.

Page No 71:

Question 16:

Answer the following in brief.
(a) Mala has a scrapyard. Her friend Anne brings in a load of iron mixed with aluminium.
How will Mala separate the iron from the aluminium?
(b) How will you separate a mixture of sand, salt and iron?
(c) How will you separate a mixture of salt and chalk?

Answer:

(a) Iron can be separated from aluminium by using a magnet. The magnet will attract iron to it and aluminium will be left behind.
(b) For separation of salt and sand, dissolve them in water. Salt will dissolve, while sand and iron will not. Filter it to separate sand and iron. Boil off the water to get salt. Iron can be separated from sand by using a magnate, to which only iron gets attracted and sand is left behind.
(c) Dissolve the mixture in water. The salt will dissolve and chalk will not. Filtration then removes the insoluble chalk from the salt solution. Boil off the water to get salt.



Page No 72:

Question 17:

State whether the following are true or false.
(a) A mixture of milk and water can be separated by filtration.
(b) A mixture of water and oil can be separated by distillation.
(c) Filtration will separate wheat from husk
(d) Camphor and sand are mixed together. By heating, camphor will sublime and the vapours can be collected. This will leave behind sand.
(e) A mixture of naphthalene and chalk powder has the smell of naphthalene.
(f) A mixture of tamarind and sugar will taste both sweet and sour.
(g) The process of loading results in better sedimentation.
(h) Sieving is the best method to separate jeera seeds form its stalk.

Answer:

(a) False. A mixture of milk and water cannot be separated by filtration.

(b) False. A mixture of water and oil can be separated by a separating funnel.

(c) False. Winnowing will separate wheat from husk.

(d) True.

(e) True.

(f) True.

(g) True.

(h) False. Winnowing is the best method to separate jeera seeds from its stalk.

Page No 72:

Question 18:

Select a suitable word from those given and write it in the space provided:
sieving, winnowing, loading, evaporation, decantation, filtration, condensation, distillation, sedimentation, sublimation
(a) After pounding, rice is separated from its husk by ______________ .
(b) A mixture of stones is allowed to fall through wire nets in order to separate them according to different sizes. This is a process of ______________ .
(c) When muddy water is kept overnight in a bucket, the clear water can be poured off from the top, next morning. This is a process of ________________ .
(d) Chilled milk is poured through a muslin cloth to remove the layer of cream. This is a process of _____________ .
(e) Salt is obtained from sea water by _____________ .
(f)  Solid iodine can be separated from sand by ____________ .
(g) _____________ is used to separate immiscible liquids.
(h) The process of settling down of heavy solid particles at the bottom of a container coantaining a mixture of a liquid and an insoluble solid is _______________ .

Answer:

(a) After pounding, rice is separated from its husk by winnowing.
(b) A mixture of stones is allowed to fall through wire nets in order to separate them according to different sizes.     This is a process of sieving.
(c) When muddy water is kept overnight in a bucket, the clear water can be poured off from the top, next morning.     This is a process of sedimentation.
(d) Chilled milk is poured through a muslin cloth to remove the layer of cream. This is a process of filtration.
(e) Salt is obtained from sea water by evaporation.
(f)  Solid iodine can be separated from sand by sublimation.
(g) Separating funnel is used to separate immiscible liquids.
(h) The process of settling down of heavy solid particles at the bottom of a container containing a mixture of a liquid and an insoluble solid is loading.

Page No 72:

Question 19:

In each of these mixtures, name the different substances present: air, sweetened lemon squash made with water, soft drinks, smog.

Answer:

Air: Oxygen,carbon dioxide, nitrogen, water vapours and various other gases.
Sweetened lemon squash made with water: Lemon,water and sugar.
Soft drinks: Water, carbon dioxide, sugar and added flavours.
Smog: Smoke and fog.

Page No 72:

Question 20:

Mention one use each of the following.
(a) filter paper
(b) separating funnel
(c) alum
(d) sieve

Answer:

(a) It is used for filtration, to separate the insoluble solid from the liquid.
(b) It is used to separate two non miscible liquids.
(c) It is used in loading.
(d) It is used to separate two solids on the bases of the difference in their sizes.

Page No 72:

Question 21:

Differentiate between these processes.
(a) sieving and winnowing
(b) distillate and filitrate
(c) solute andsolvent
(d) homogeneous and heterogeneous mixtures

Answer:

(a)

Sieving Winnowing
It is the method of separation which is based on difference in sizes of the components of the mixture It is the method of separation based on difference in weights of components of the mixture
 For example: It is used to separate sand from stones.  For example: It is used to separate husk from grains.
 


(b)
Distillate Filtrate
The pure liquid obtained after distillation is called distillate. The clear liquid obtained after filtration is called filtrate.



(c)
Solute Solvent
Solute is the substance which gets dissolved. Solvent is the liquid in which solute is dissolved.
 
(d)
Homogeneous mixture Heterogeneous mixture
The mixture in which the components are evenly distributed are called homogenous mixture. The mixture in which components are unevenly distributed are called heterogeneous mixture
Example: Alloys Example: Crude oil

Page No 72:

Question 22:

Give reasons to explain these statements.
(a) Sugar is a pure substance whereas sugar solution is a mixture.
(b) Pure iron cannot be used for construction of buildings.
(c) Decantation cannot be used to separate a mixture of salt and water.
(d) Many people sprinkle water in their courtyard after a sandstorm.

Answer:

(a) Sugar is pure, as it has only one component, i.e., sugar. Sugar solution is a mixture, as it has sugar and water.
(b) Pure iron cannot be used for the construction of buildings, as it will get rusted.
(c) Salt is soluble in water. Decantation only separates insoluble solids that settle on the bottom; thus, it cannot be used to separate a mixture of salt and water.
(d) Many people sprinkle water in their courtyard after a sandstorm so that the sand particles settle down.

Page No 72:

Question 23:

Define the following:
(a) alloy
(b) saturated solution
(c) loading

Answer:

(a) Alloy: It is a mixture of one or more metals with another element which could be a metal or a non-metal.
(b) Saturated Solution: The solution in which no more solute can be dissolved at a given temperature, is termed as a saturated solution.
(c) Loading: It is the process of making light impurities heavy by adding insoluble substances (like alum) so that they settle down.



Page No 73:

Question 24:

Name the method of separation involved in each example given below.
(a) When it rains, the raindrops attach themselves to the dust in the air. This makes the dust particles heavy and brings them down to the ground. Because of this, the air becomes clearer.
(b) A mixture of water and mustard oil which are miscible are separated.
(c) Salt is separated from its mixture in water, so that the water is not lost.
(d) Rice is separated from its husk.
(e) A cook while washing rice found that the rice grains settled to the bottom of the vessel. He then drained out the top layer of water containing lighter dust particles. The rice was then transferred to a strainer to remove the excess water.
(f) Salt is separated from sea water.
(g) Sand is separated from gravel at a construction site.

Answer:

(a) Loading
(b) Separating funnel
(c) Distillation
(d) Winnowing
(e) Decantation
(f) Evaporation/heating
(g) Sieving

Page No 73:

Question 25:

Explain how these mixtures can be separated.
(a) kerosene from a mixture of kerosene and water
(b) water from a mixture of haldi and water

Answer:

(a) Kerosene can be separated from a mixture of kerosene and water by a separating funnel as they are immiscible.     Add the mixture in the separating funnel and let it stand. The kerosene will float on water. The tap is then turned on     to allow the water to flow, and is turned off when most of the water is taken out, leaving the kerosene behind.
(b) The mixture of haldi and water can be separated by the method of decantation. Allow the mixture to stand in a     beaker so that haldi settles down at the bottom, then decant the water in another beaker, leaving the haldi behind.

Page No 73:

Question 26:

Why do we need to separate mixtures? Give three examples to explain your answer.

Answer:

We need to separate mixtures to extract a pure substance out from them. For example, to obtain pure water from a salt water solution, to separate grains from husk, to separate cream from milk.

Page No 73:

Question 27:

This apparatus can be used to separate a mixture of water and mustard oil.
Label the diagram and name the apparatus used in this process.
Figure

Answer:

The apparatus is a separating funnel.

Page No 73:

Question 28:

The apparatus shown below can be used to obtain pure water from salt water.
(a) Label the diagram from i to vi.
(b) Why is it necessary to use the ice?
(c) Describe how this method works.
(d) What is this method of separation called?
Figure

Answer:

(a) i- distilling flask, ii- salt solution, iii- cork, iv- ice, v- condenser beaker, vi- pure water.
(b) Using ice is important to condense the water.
(c) The salt solution is heated in the flask till it boils and steam rises up. The steam then passes through the condenser     and solute is left behind in the beaker. Steam is condensed in the beaker and pure water is collected.
(d) This is called distillation.

Page No 73:

Question 29:

Choose the correct word from the circle in the middle and write it next to the clues given around it.
Figure

Answer:

Used to separate insoluble solid particles from liquid: Filtration
Used to separate particles of different sizes: Sieving
Used to separate heavy and light particles: Winnowing
Used to separate dissolved substance from their solution: Distillation



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