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Chapter Review:

• Methods of separating substances are Handpicking, winnowing, sieving, sedimentation, decantation and filtration.
• Husk and stones could be separated from grains by handpicking.
• 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.
• A saturated solution is one in which more of that substance can be dissolved.
• Separation methods is used to remove or picked out unwanted substances from mixtures.
• A solution is prepared by dissolving a substance in a liquid.
• The separated husk is used for many purposes such as fodder for cattles.
• Winnowing is commonly used by farmers to separate lighter husk particles from heavier seeds of grain

Exercise (NCERT Text Book)

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

Ans: A mixture has many impurities and unwanted substances like stone, husk and other materials. These unwanted materials only can be removed by separating methods.

Ex : husk from grains and water from salt.

Q2: What is winnowing? Where is it used?

Ans: Winnowing is a method of separation. It is used to separate heavier and lighter components of a mixture by wind or by blowing air.

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

Ans: By using Sieving Method.

Q4: What is sieving? Where is it used?

Ans: Sieving is method of separating in which a sieve  is used to separate the components of mixture. It is used when components of a mixture have different sizes.

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

Ans: By using the sedimentation and decantation methods.

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

Ans: Yes It can be separated by using sieving method these can be easily separated.

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

Ans: By using the sedimentation and decantation methods.

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 ___________.

Ans:

1. Threshing
2. Centrifugation
3. Evaporation
4. Sedimentation

Q9: True or false?

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

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

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

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

Ans:

1. False
2. True
3. False
4. False

Important Questions with solution

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Q1: What is mixture? Give some examples.

Ans: Things that are made of two or more than two substances are known as mixture. Examples – air, dust particles, Sherbet etc; 

Q2: Define Separation.

Ans:  By various methods a mixture is separated into its components is known as separation.

Q3: What is Sedimentation?

Ans: The settling down of heavy solid particles from the liquid in a mixture of solid and liquid substances is known as sedimentation.

Q4: What is decantation?

Ans:  The process of separating a solid from a liquid by pouring out the liquid is known as decantation.

Q5:  What is filtration?

Ans:  It is a method of separating specific particles from a liquid mixture by passing it through a porous membrane.

Q6:  What is sublimation?

Ans: Direct conversion of a solid into gas or gas into a solid, this process of conversion is called sublimation.

Q7: Some solid substances have property to covert directly into vapour on heating without being converted back into a liquid.

1. What is called this process?
2.  Name some such substances.
3. What happens when cooled the vapour?

Ans:      

1. This process is called sublimation.
2. Ammonium Chloride, Camphor, Naphthalene etc;
3. when cooled the vapour it gets converted directly into a solid.

Q8:  What is evaporation? What is its used ?

Ans: Conversion of water into water vapour is known as evaporation. It is used for separating salty or water soluble substances from water. Such as salt from sea.

Q9:  How will you separate salt from a mixture of Ammonium Chloride?

Ans: The method sublimation will be used for separating salt from a mixture of Ammonium Chloride. On heating Ammonium Chloride gets converted directly into vapour, and salt remains in the pot. 

Q10:  How can straw be separated from wheat grains?

Ans: Winnowing.

Q11:  How can a mixture of sand and marble chips be separated?

Ans:  Sieving.

Q12:  How can clean water be separated from muddy water?

Ans:  Sedimentation and loading.

Q13: There is given a mixture of wood powder, iron nails, sand, and iron fillings. Which process of separation would you use to separate the iron things?

Ans:  Magnetic separation

Q14: What type of substances can be separated by sieves/ sieving method?

Ans: Substances of two solids of different size can be separated by sieves/ sieving method like flour.   

Important Questions with solution

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Q1: What is saturated solution?

Ans: The solution in which no more substances can be dissolved in the amount of water we have taken. The solution is now said to be saturated solution.

Q2: What is the used of separated husk of wheat grain?

Ans :  separated husk of wheat grain is used for many purposes such as fodder for cattles.

Q3: What makes the winnowing success?

Ans: The wind makes the winnowing success.

Q4: What is used to thresh large quantities of grain.

Ans: threshing machine.

Q5:  What kinds of elements of mixture can be separated by hand picking method?

Ans: This method of handpicking can be used for separating slightly larger sized impurities like the pieces of dirt, stone, and husk from wheat, rice or pulses.