Question

Which liquid has maximum surface tension?
A. Water
B. Alcohol
C. Ammonia
D. Glycerol

Answer 1

Surface tension is the tendency of the liquid surfaces to shrink in such a way that they acquire a minimum possible surface area. It is generally defined as the force applied per unit length or the energy per unit surface area and is the property responsible for the movement of insects on the surface of any liquid.

Complete step by step answer:
Because of the relatively high forces of attraction among the water molecules due to a web of hydrogen bonds, water has a higher surface tension than most other liquids. Surface tension is an important factor in the phenomenon of capillarity. Due to the cohesive forces present in the liquid, a molecule is pulled equally in every direction by neighboring liquid molecules, resulting in a net force of zero. The molecules at the surface do not have the same molecules on all sides of them and therefore are pulled inward. This creates some internal pressure and forces liquid surfaces to contract to the minimum area.
In the case of water, the cohesive forces are generally the hydrogen bonds and they create a great web like structure that binds the water molecules to move haphazardly in the system. This is not true in the case of alcohol, ammonia and glycerol. Their surface area does not fall as low as that of the water.

Thus, the correct option is A. Water.

Note: There is also a tension parallel to the surface at the liquid-air interface which will resist an external force, due to the cohesive nature of water molecules. The forces of attraction acting between the molecules of the same type are called cohesive forces while those acting between the molecules of different types are called adhesive forces.