The water molecule is composed of two hydrogen atoms and one oxygen atom joined by a covalent bond. That is, the two hydrogen atoms and the oxygen atom are bonded together by sharing electrons. Its formula is H2O.
Changes of status
This animation shows what happens when heat is applied to a block of ice. Notice that the temperature increases until it reaches 0ºC, where it remains stable while the ice melts. The same thing happens at 100°C as the liquid water evaporates.
Electrolysis of water
The electrolysis of water is the decomposition of water (H2O) into the gases oxygen (O2) and hydrogen (H2) by means of a direct electric current. To reduce the resistance to the passage of current through water, it is usually acidified by adding a small amount of sulfuric acid or by adding a strong electrolyte such as sodium hydroxide, NaOH.