Water, water, everywhere, but...

Puddles in the road on a rainy day, ponds and lakes in the park, streams, rivers and even the sea - water is everywhere. But it is so ubiquitous that we often fail to notice its very varied chemistry.

The lily leaf (fig 1), has had its surface splashed by rainwater or a nearby fountain. The drops of water are almost spherical in shape, except one running down a gentle slope. There is no attraction between the waxy surface of the leaf and the water. The surface tension of the water acts almost like a skin pulling the drop so as to minimise its surface area. 

This force results from the hydrogen bonds which join the water molecules together. They are not very strong but they are certainly stronger than the van der Waals' forces which attract most other molecules to each other.