Problem: Meniscus shapes for water and mercury in glass tubes.If the inside surface of each tube were coated with wax, would the general shape of the water meniscus change? Would the general shape of the mercury meniscus change?

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We are asked to determine if the water or mercury meniscus changes when the inside surface of the tube is coated with wax following the figure:

A photograph shows two test tubes side by side. One holds water and the other holds mercury. The meniscus or surface of the water is concave, forming a cup shape, while the meniscus of the mercury is convex, meaning it bulges upward. Molecular view diagrams show that in the water test tube, water molecules form hydrogen bonds both with the test tube glass walls (adhesive forces) and with each other (cohesive forces). Because adhesive is greater than cohesive, H2O molecules adhere to the wall more than to each other, forming a concave surface. In the mercury test tube, mercury molecules form mercury–mercury cohesive forces. Because cohesive is greater than adhesive, mercury atoms at the surface adhere to the wall less than to each other, forming a convex surface.

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Problem Details


A photograph shows two test tubes side by side. One holds water and the other holds mercury. The meniscus or surface of the water is concave, forming a cup shape, while the meniscus of the mercury is convex, meaning it bulges upward. Molecular view diagrams show that in the water test tube, water molecules form hydrogen bonds both with the test tube glass walls (adhesive forces) and with each other (cohesive forces). Because adhesive is greater than cohesive, H2O molecules adhere to the wall more than to each other, forming a concave surface. In the mercury test tube, mercury molecules form mercury–mercury cohesive forces. Because cohesive is greater than adhesive, mercury atoms at the surface adhere to the wall less than to each other, forming a convex surface.

Meniscus shapes for water and mercury in glass tubes.


If the inside surface of each tube were coated with wax, would the general shape of the water meniscus change? Would the general shape of the mercury meniscus change?

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Intermolecular Forces and Physical Properties concept. If you need more Intermolecular Forces and Physical Properties practice, you can also practice Intermolecular Forces and Physical Properties practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Scerri's class at UCLA.