question_answer

  Manu went to watch movie with his parents. In the dark, he found a small beam of light within which million of tiny particles were dancing. He thought, when their was lights, no such a beam appears. He was very surprised. He asked about this from his science teacher. His science teacher told him that was due to scattering of light.                                  Answer the following questions based on the above passage. (i) What values are exhibited by Manu? (ii) What were the tiny particles? (iii) Why these were not appeared in the presence of light? (iv) What a single term can be used for scattering of light of such particles? (v) Give an another example of Tyndall effect.

Answer:

                  (i) Dissolve copper sulphate in water.    (1/2) Add few drops of dil.  to get clear solution.                                                         (1/2) Heat the solution in China dish till crystallisation point is reached.              (1/2) Cool this saturated solution.                    (1/2) Crystals of pure copper sulphate are formed. Impurities remain behind in the solution. (1/2) Separate these crystals from solution by filtration and dry.                                        (1/2) (ii) It is used to purify solids.                    (1) (iii) Soluble impurities can be removed by this tech-nique which are not removed by evaporation.                                                      (1)