Water

Water is the state of the H₂O molecule that we know best. Because water is a small molecule, it’s unusual in that it’s in liquid form at room temperature.

Creative Commons Image Maigh via Flickr
A swimming pool [Image: Maigh under CC-BY-NC-ND licence]

For a molecule of this size one would expect it to be a gas. The secret is in the hydrogen bonding.

Unlike in its frozen form of ice, the hydrogen bonds in water do not create rigid structures, but create molecules that "cluster" together.

These clusters of four molecules can link to others. The clusters are continually forming and breaking apart every few picoseconds.

The molecules are in constant motion. The blue colour of water is also a result of the hydrogen bonds.

As the molecule vibrates, it drags and pushes against its neighbours, absorbing a little red light, leaving a bluish hue in the light that remains.