Wed January 25, 2012 By:

why is the shape of water meniscus concave while that of mercury meniscus is convex?

Expert Reply
Thu January 26, 2012
It is due to what is called cohesion and adhesion. The water molecules are attracted to each other through cohesion, which is the attraction between similar particles. Adhesion is attraction between unlike molecules. When water is placed in a glass container, the adhesive forces between the water and the tube are stronger than the cohesive forces between the water molecules, and the water climbs up the glass. Conversely, the attraction between mercury atoms (cohesion) is stronger than its attraction to the glass (adhesion). Therefore, the atoms pull together and away from the glass.
Hence, shape of water meniscus is concave while that of mercury meniscus is convex.
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