Water meniscus

Water wets glass. The forces of adhesion between the glass and the water molecules exceeds the forces of cohesion between the water molecules themselves and the water climbs up the vertical glass wall. The curve at the wall (or between two closely spaced walls) is called a meniscus.

The formation of a meniscus has several consequences of which two are noteworthy.

1 A measuring cylinder is read to the bottom of the meniscus.

2 Water will rise in a narrow tube due to the upward pull of surface tension forces. The effect is called capillary action and is of singular importance for biological systems. In particular capillary action transports ground water to the tops of tall trees and water soaks into cloth and paper. Image