Separation of Substances (part -2) class 6


Separation of Substances

Q.7. Write a short note on each:
      Sedimentation, Decantation and Filteration
Ans. 
Sedimentation
  • When the heavier insoluble component in a mixture settles after water is added to it, the process is called sedimentation.
  • This method works on the differences in densities of two components of a mixture.
  • The heavier insoluble component that settles at the bottom is called sediment.
  • The clear liquid that remains above the sediments is called supernatant.
  • For example: Impurities settles at the bottom when muddy water is kept overnight in a bucket. 
                                           
Decantation
  • The process of pouring out the supernatant slowly to another container without disturbing the sediments is called decantation.
  • For example: The clear water is poured off slowly from the top of the bucket having impurities settled at the bottom.
                                         
Filteration
  • This is  a method of separation of insoluble solid from liquid using a net like structure, called filter. 
  • The mixture is poured on the filter. The insoluble solid remains on the filter and is called residue.
  • The liquid that comes down after passing through the pores of filter is called filterate.
  • For example: separating tea leaves from prepared tea by a strainer.
                                                        
Q.8. How will you separate oil and water from their mixture? 
Ans. The same principle of sedimentation and decantation is used for separating a mixture of two liquids that do not mix with each other. 
For example, oil and water from their mixture can be separated by this process. If a mixture of such liquids is allowed to stand for some time, they form two separate layers due to sedimenatation. The component that forms the top layer can then be separated by decantation. 

Q.9. A piece of cloth can be used as filter. How?
Ans. In a piece of cloth, small holes or pores remain in between the woven threads. These pores in a cloth can be used as a filter.
Q.10. What is filter paper? How should we use it?
Ans. A filter paper is one such filter that has very fine pores in it. The steps involved in using a filter paper are:
  • A filter paper folded in the form of a cone is fixed onto a funnel.
  • The mixture is then poured on the filter paper.
  • Solid particles in the mixture do not pass through it and remain on the filter.
                      



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