The Boiling Point of Water

The Boiling Point of Water

The simple answer is 100º Celsius, however that depends on where you are and the oxygen content of the water. To explain this better we should look at the molecular structure of H2O. It is a polar covalent bond meaning the oxygen is in the centre and shares one electron with each of the hydrogen's one electron. As there is an unequal amount of electrons this causes a dipole effect giving the hydrogen molecules a small positive charge and the oxygen slightly negative, resulting in a bent shaped molecule. This hydrogen bonding is important in giving water its unique properties and explains why the molecules are attracted to each other (see Figure1)

Figure 1, Hydrogen Bonding

Water is said to be something of an anomaly as compared to other substance it has a very high boiling point and a very low freezing point. This type of hydrogen bonding needs a lot of energy in order turn from a liquid to a gas. As humans we are mostly water and investigation of its properties has long since been undertaken.

" In 1741, Anders Celsius defined his temperature scale on the melting and boiling temperature of water. Although Celsius did not discover the thermometer - both Philo and Hero of Alexandria (who also mentioned steam power in 50 BC) described such a principle - his design was much more precise than any previous such invention. Celsius scaled his measurements as 0 for boiling point and 100 for freezing point but the order was later reversed." (Didyouknow.org (1908) Boiling point of water. [online] Available at: http://didyouknow.org/celsius/ [Accessed: 26 Oct 2012])

So while water will boil at 100ºC at sea level, it will boil at lower temperatures depending on atmospheric pressure, for instance, in Denver, Colorado which is about a mile above sea level, water is known to boil at 95º/96ºC. The bubbling itself is caused by the kinetic energy of the molecules being turned to a gas from the heat applied.