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8th Class Science Combustion and Flame Question Bank Combustion and Flame Formative Objective Problems

  • question_answer
    Two friends Gaurav and Samik took two glass plates and two lighted candles. Gaurav held the glass plate inside the flame of the candle and Samik held it slightly above the candle flame. Which of the following statements is correct?

    A)  Both Gaurav's and Samik's glass plates will get blackish soot deposition.

    B)  Neither Samik's nor Gaurav's glass plate will have blackish soot deposition.

    C)  Gaurav's glass plate will have blackish soot deposition but Samik's glass plate will not.

    D)  Samik's glass plate will have blackish soot deposition but Gaurav's glass plate will not

    Correct Answer: C

    Solution :

      Gaurav held the glass plate inside the flame. Therefore, he held the plate in the luminous zone. This zone is the zone of incomplete combustion. Therefore, a circular blackish ring will be obtained on his glass plate. Samik held the glass plate slightly above the flame i.e., in the non-luminous zone. As this zone is the zone of complete combustion, no soot deposit will take place in this case. The correct answer is C.


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