properties of water

Authors Avatar

Water – properties and importance

Water is the most important molecule on the Earth.  It provides a basis for all living life and makes up between 75%-90% of the total mass of a cell.  Some animals such as jellyfish are made up of 96% water.  75% of the total of Earth’s surface is covered with water.  

Water is a simple molecule made of 2 hydrogen atoms and one oxygen atom, H20. The hydrogen and oxygen atoms are bonded covalently.  Water is not a linear molecule; the two hydrogen atoms form a bond with the oxygen at the angle of 104.5 degrees.

Its properties allow it to act as a solvent, a reactant, as a molecule with a consistent properties, as an environment and as a temperature stabiliser.

With water, the large number of protons in the oxygen nucleus have a stronger attraction for these shared electrons than the comparatively tiny hydrogen nuclei. This pulls the electrons slightly closer to the oxygen nucleus and away from the hydrogen so that the oxygen develops a slight negative charge and the hydrogen's a slight positive charge. This makes the molecules slightly polar.

Water can dissolve polar or ionic substances and can keep them in solution because of water's own polar properties. Substances that dissolve in water are known as hydrophilic substances (eg: sugar). Ionic substances such as sodium chloride (NaCl) are made up of positive and negative ions. Sodium chloride is held in it's structure by the strong attraction between it's positive sodium ions and negative chloride ions. Normally these ionic attractions require a large amount of energy to break but when put into water the negative oxygen side of the water molecules cluster around the positive sodium ions Na+ and the positive hydrogen atoms cluster around the negative chloride ions Cl-. The attraction between the Na+ and Cl- ions is weakened as the ions are separated.

Join now!

Water can also separate covalently bonded molecules such as glucose and sucrose because the polar hydroxyl groups (-OH) in its structure forms hydrogen bonds with the water separating the molecules from each other.  Water's properties as a solvent are vital to life as most biochemical reactions such as respiration occur in solution. This is why cell cytoplasm contains about 90% water. Water cannot dissolve hydrophobic substances such as fats and oils (see diagram), these are used by organisms as cell membranes to separate cells and also as waterproofing as they prevent water from entering the organism if it is ...

This is a preview of the whole essay