Short Q & A:
Q1: What is done in threshing? How it can be done?
Ans: In threshing, the stalks are beaten to free the grain seeds. Threshing can be done with the help of bullocks or machines.
Q2: Which type of impurities can be separated by hand picking?
Ans: Hand picking is used to separate slightly large sized impurities. It is used when the quantity of impurities is not very large.
Q3: Why is separating different components of a mixture necessary?
a). To separate two different but useful components.
b). To remove impurities or non useful component from a mixture.
Q4: What do you mean by winnowing? Explain with example.
Ans: Winnowing is separating the heavier and lighter components of a mixture by wind or by blowing air. For example-separating mixture of saw dust and sand.
Q5: How is sieving use to separate particles of a mixture? Give example.
Ans: Sieving allows the fine particles to pass through the holes of a sieve while bigger impurities remain on sieve. E.g. separating bran from flour.
Q6: What is a saturated solution?
Ans: When no more solute (e.g. Salt) can be dissolved in the amount of solvent (e.g. Water) taken, the solution is said to be saturated solution.
Q7: What happens when steam comes in contact with the metal plate cooled with ice?
Ans: When steam comes in contact with the metal plate cooled with ice, it condenses and forms liquid water.
Q8: What is condensation?
Ans: The process of conversation of water vapour into its liquid form is called condensation.
Q9: By which process salt, sand and water can be separated?
Ans: Salt, sand and water can be separated by decantation, filtration, evaporation followed by condensation.
Q10: What is the difference between evaporation and condensation?
Ans: The process of conversion of water into its vapour is called evaporation.The process of conversation of water vapour into its liquid form is called condensation.
Q11: What is sedimentation?
Ans: When the heavier component of a mixture settles after water is added to it, the process is called sedimentation.
Q12: Write the name of method for separating-
a) Salt from salt water solution.
b) Wheat from mixture of wheat and rice.
Q13: Which of the following is true :
a) Flour is sieved to separate impurities.
b) Threshing is used to separate grains from stalk.
c) Winnowing is used to separate component of same weight.
Long Q & A:
Q1: How is common salt obtained from sea?
Ans : Sea water contains many salts mixed in it. When sea water is allowed to stand in shallow pits, water gets heated by sunlight and slowly turns into water vapour, through evaporation. In few days water is evaporated completely leaving behind solid salts. common salt is obtained from mixture of salts by further purification.