How do ants manage to float on water?

            Ants manage to float on water due to an interesting property, known as surface tension, of liquids. In any liquid, the constituent molecules are in constant motion. They slide over one another, maintaining some freedom of motion while exhibiting enough attractive force to hold the molecules close to each other. This enables the liquid to flow.

            But the attractive forces in a column of liquid are not the same at all points. Molecules at the centre of the liquid are subjected to uniform forces all around. But a molecule at the surface is subjected to unbalanced forces. Strong attractive forces exerted by the molecules amongst themselves pull the liquid inwards. That means, the molecules at the surface feel an excessive force pulling inwards. The net result is that the liquid behaves as though it has an invisible elastic ‘skin’ which always tries to contract and decrease the surface area. This contractive force on the surface of the liquid is called surface tension.

            Now let us come to the actual question: Ants are so light that their weight is not sufficient to overcome the surface tension and break the contracting forces. If the weight of an ant is, then it will break the elastic membrane and sink. Similar observations can be made by placing a greased needle on a blotting paper which in turn is placed on water. The blotting paper will absorb the water and sink. But the needle floats.