Like all natural matter, water consists of molecules. If you study a drop of water under the microscope and magnify it a million times, you will notice such molecules. The building blocks of the molecule are hydrogen (H) and oxygen (O). As two hydrogen atoms bind one oxygen atom at a time, the molecule gets the chemical formula H₂O. If you picture these two atoms as building blocks, they behave like the parts for building a model car, which fall apart if there is no firm connection. You will need glue. In the water molecule, the electrons each atom possesses, take charge of this task ensuring that the atoms are firmly connected through the electrons.

If you look at the two oxygen and hydrogen atoms in the picture above more closely, you will immediately notice that the atoms are of a different size. The oxygen atom (blue) is much bigger than the hydrogen atoms (grey). The oxygen atom is bigger and therefore 'stronger' and takes the electrons away from the smaller hydrogen atoms. As electrons are negatively charged particles, the oxygen atom becomes negatively charged, too. The hydrogen atoms, which lack the electrons, become positively charged. Such a molecule is called a dipole.

But Why Is Water Liquid?

As explained above, the water molecule consists of a positively and a negatively charged part. Because of the attraction of positive and negative charges, each water molecule binds to another water molecule. This bond is called a hydrogen bond. Due to the formation of these hydrogen bonds the water molecules are no longer able to move freely. They form three dimensional, linked structures, called clusters. The restriction on the movement of the water molecules is the reason why water is liquid.

Since the hydrogen bonds are very stable, and generally a lot of energy is necessary to break them up, water can be used in many ways. If the water molecules didn’t have the ability to form hydrogen bonds, there would be no fluid water on earth.