SSC General Science & Technology Sample Paper NCERT Sample Paper-3

  • question_answer
    On clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because:

    A)  Cohesion of water is greater than its adhesion with glass

    B)  Mercury is a metal

    C)  Cohesion of mercury is greater than its adhesion with glass

    D)  Density of mercury is greater than that of water

    Correct Answer: C

    Solution :

    [c] Mercury in a glass flask is a good example of the effects of the ratio between cohesive and adhesive forces. Because of its high cohesion and low adhesion to the glass, mercury does not spread out to cover the top of the flask, and if enough is placed in the flask to cover the bottom, it exhibits a strongly convex meniscus, whereas the meniscus of water is concave. Mercury will not wet the glass, unlike water and many other liquids, and if the glass is tipped, it will roll around inside.

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