Meniscus

The term "meniscus" refers to the curved surface of a liquid in a container. It is the shape assumed by the liquid's surface due to the intermolecular forces between the liquid molecules and the container's walls.


When a liquid is placed in a container, such as a beaker or a test tube, its surface tends to curve either upwards or downwards at the edges where it meets the container. This curvature is known as the meniscus. The shape of the meniscus depends on various factors, including the nature of the liquid, the material of the container, and the adhesive or cohesive forces between the liquid molecules.


The meniscus can be concave or convex. A concave meniscus occurs when the adhesive forces between the liquid and the container are stronger than the cohesive forces between the liquid molecules. This results in the liquid surface curving downwards at the edges. Water is an example of a liquid that typically forms a concave meniscus in glass containers.


On the other hand, a convex meniscus occurs when the cohesive forces between the liquid molecules are stronger than the adhesive forces between the liquid and the container. This causes the liquid surface to curve upwards at the edges. Mercury is an example of a liquid that forms a convex meniscus in glass containers.


The shape of the meniscus is important in various experimental measurements, such as determining the volume of a liquid in a graduated cylinder. It is necessary to take the reading at the bottom of the meniscus for accurate measurements.