Water

The combination of the two chemical elements hydrogen (H) and oxygen (O) makes Water (H2O). In solid state water is defined as ice, in gaseous state as water vapour/vapour. Water shows the highest density at +4 °C (≙ 39.2 °F). For this reason ice swims on water, i.e. water accumulations start freezing always from the surface, whether puddle or sea. This phenomenon is called Anomaly of Water.