The chemical reactions of all living things take place in an aqueous solution. This makes water indispensable to life. The shape of the water molecule causes one side of the molecule to be slightly positively charged and the other side to be negatively charged. A molecule with an uneven charge pattern is known as a polar molecule . Even though the total charge of the subatomic particles within a polar molecule is balanced, the shape of the molecule causes one area to be slightly positive while another area is slightly positive.
Water is a polar molecule because the two hydrogen atoms are slightly to one side of the molecule.
In the diagram above, the oxygen atom in each water molecule is red and the two hydrogen atoms are blue. The red side of the molecule is slightly negative and the blue side is slightly positive. You can see in the diagram how the positive side of one molecule aligns with the negative side of another. The polar nature of water makes it very effective in dissolving other substances. Water must gain or lose a relatively large amount of energy for its temperature to change.