What is a meniscus?

• A. A device that measures mass
• B. The curved upper surface of a liquid in a tube
• C. A color change indicator
• D. The volume of a liquid

Answer: (B)

A meniscus is the curved surface the liquid forms inside a narrow tube because of the liquid’s cohesion and its attraction to the tube walls. This curved surface is what you use to read the liquid’s volume in glassware—after all, the level you read depends on the shape of that surface. For water in a glass tube, the curve is concave (bottom of the curve at the center), and you read at that bottom point for an accurate volume. This concept isn’t about a device for measuring mass, a color-change indicator, or the amount of liquid itself; it’s about the shape of the liquid surface in a tube.