Basic chemistry help for students and teachers


Water, H2O

Water is a simple compound with a set of unique properties that are essential for life.

The chemical formula for water is H2O and its proper chemical name is dihydrogen monoxide. Water contains two parts hydrogen to one part oxygen. The ratio of these elements determines the molecular formula.

When broken down by electrolysis water produces two parts hydrogen gas to one part oxygen gas. Electrolysis is the process of using electricity to produce a chemical reaction.

2H2O(l) =electrolysis=> 2H2(g)  + 1O2(g)

Water is an excellent solvent for ionic compounds like salt and for polar compounds like sugar. In living things water allows materials to dissolve and interact in the many chemical reactions which take place in cell that are essential life. eg. Cellular respiration.

Water freezes at 0°C and boils at 100°C at 1 atmosphere pressure.

As a solid, water forms a hexagonal arrangement between the water molecules and takes up more space than when a liquid. This means that ice is less dense than water and floats to the top. When a lake freezes, it freezes at the surface first producing a protective layer which insulates the water below and helps preserves life below.


The oxygen atom in the water molecule is surrounded by four pairs of electrons which repel each other producing a tetrahedral arrangement. Two of the pairs of electrons are bonded to hydrogen atoms and the other two pairs of lone electrons are unbonded.

This means that the water molecule is not linear. Water is a V-shaped molecule and is highly polar in nature.