Surface tension

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WATER IS STICKY!

Surface tension is an important property of water in which the molecules are attracted to each other and stick together. These properties are called

adhesion and cohesion

The adhesive and cohesive properties of water molecules enable insects to ‘walk on water’, rain to form droplets and beads of water to form on leaves and other surfaces, such as on a car when it is washed, on a tent when camping or on umbrellas in the rain. It is also how plants drink up water from the ground through their root system.

Water molecular structure

Water is made up of one oxygen atom and two hydrogen atoms. These atoms have positive (+) and negative (–) charges

Water strider

Water droplets on leaf

Car wash

The charges are why the atoms are attracted to each other. They ‘stick’ together because they have hydrogen bonds

SURFACE TENSION

These charges and bonds are the reason the two hydrogen atoms and one oxygen atom are attracted to each other to form a water molecule. It is also the reason the water molecules ‘stick’ to each other creating properties like surface tension.

Surface water molecules

Water molecule charges

DID YOU KNOW?

Pond skaters – also called water striders – are aquatic insects that have long legs and hairy feet. These features enable them to ‘walk on water’.

Male pond skaters can use their legs to talk to each other by vibrating the surface of the water. They make high-frequency ripples to signal a warning to other males if they enter their territory or are trying to compete with them for food.