What is water?

Water is made up of molecules. These molecules are made up of two hydrogen atoms (H2) and one oxygen atom (O). This is why it is scientifically called H2O.

Water is the most common substance found on the earth’s surface and it is the only substance found naturally in three forms:

  • solid (as ice)
  • liquid (as water)
  • gas (as water vapour). 

Water exists in all these three forms at 0.01°C. Which you have to admit is cool!

The density of water is approximately 1g/cm³.  As water cools it becomes increasingly dense. The maximum density of water is 4ºC. As water is cooled further becomes less dense. This property is why ice floats. This impacts the ecosystems of freshwater lakes because it is unlikely that deep lakes will completely freeze.

As water is heated the molecules become agitated, boiling at 100’C turning from a liquid into a gas. At higher altitudes due to the increased pressure the boiling point is lower.