Cohesiveness and Surface Tension

Water flows freely, yet water molecules do not break apart. They cling together particularly to polar surfaces. Therefore, water can fill a tubular vessel and still flow so that dissolved and suspended molecules are evenly dispersed throughout the water body. For these reasons, water is an excellent transport medium both outside and within living organisms. The surface tension of water is very high as compared to other liquids except mercury. The role of surface tension is obvious. Certain objects such as pollen and dust float at the surface of water even though they are denser, due to its high surface tension. For similar reasons significant amount of water is retained by the soil through capillary attraction for plant growth.