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Describe the intra- and intermolecular forces of water molecules. How do these forces relate to their importance in biology? Support your answer with two examples.

Solution

If two atoms share electrons, in order to have a completely filled outer shell then the bond formed between the two atoms is called, covalent bond. Covalent bond is the strongest of all the chemical bonds.

In a covalent bond, if the electrons are not shared equally, then it induces partial charge on each atom, such a type of bond is called, “polar covalent bond.” For example, in water molecule, the two hydrogen atoms share electrons with the more electrophilic oxygen atom. So, the electron pair spend most of the time towards the nucleus of the oxygen atom than the hydrogen nucleus.

Due of the presence of hydrogen bonds and strong intermolecular forces, water has high specific heat index. Specific heat capacity of water is defined as; the amount of heat (energy in joules) required for raise of temperature of water per unit mass by 1⁰C. The specific heat capacity of water is 4.18Joules. So, body can lose heat by perspiration.

Because of the high heat capacity of water, water can absorb more amount of heat before raising its temperature. So, it has high boiling point. And also, it slowly looses the heat before it is going to get cooled, so it has low freezing point. Thus, the temperature of water falls and rises slowly due to its high heat capacity. It helps to maintain body temperature.

Because of the hydrogen bonding, water exhibits high surface tension. So, water molecules on the surface are more strongly attracted to each other than to the air above. This is necessary for the functioning of alveoli. The layer of moisture over the alveoli is necessary for the gaseous exchange.

Due to the polar nature of water, water can dissolve inorganic salts that dissociate into ions in the presence of water (like dissolves like). So, the blood can carry many of the water soluble substances throughout the body. Water cannot dissolve nonpolar substances; they are dissolved in non-polar solvents like benzene.