Master the Science of Surface Tension with This Quiz!

Surface tension is caused by cohesive forces between molecules of a liquid, resulting in a net force of zero for molecules away from the surface and forces causing the surface to contract. The balance between cohesion and adhesion determines the degree of wetting and shape of meniscus. Surface tension is responsible for the shape of liquid droplets, which tend to be pulled into a spherical shape by the imbalance in cohesive forces. Surface tension can be defined in terms of force or energy and is measured in force per unit length. It is proportional to the force required to increase the surface area and is equal to the ratio of the force required to stop a movable side from sliding to the length of the immobile side. It is also equal to the ratio of the change in energy of the liquid to the change in surface area of the liquid.Surface tension is a measure of the cohesive forces that hold the molecules of a liquid together. It can be measured in SI system as joules per square meter and in the cgs system as ergs per cm2. The work done to increase the surface area of a liquid is stored as potential energy. A free droplet of liquid assumes a spherical shape which has the minimum surface area for a given volume. The equivalence of measurement of energy per unit area to force per unit length can be proven by dimensional analysis. There are several methods to measure surface tension which include the drop weight method, capillary rise method, maximum bubble pressure method, and Wilhelmy plate method. Water has a surface tension of 72.8 mN/m at 20°C. Surface tension has effects on various natural phenomena such as capillary action, wetting, and flotation.