Properties and uses of water
Water is essential to living organisms. The list below shows some of its properties and uses.
Hydrogen bonds are formed between the oxygen of one water molecule and the hydrogen of another. As a result of this water molecules have an attraction for each other known as cohesion.
Cohesion is responsible for surface tension which enables aquatic insects like pond skaters to walk on a pond surface. It also aids capillarity, the way in which water moves through xylem in plants.
Water is a dipolar molecule, which means that the oxygen has a slight negative charge at one end of the molecule, and each hydrogen a slight positive charge at the other end. Try to learn all of the functions of water molecules given in the list. Water is used in so many ways that the
chance of being questioned on the topic is high.
Other polar molecules dissolve in water. The different charges on these molecules enable them to fit into water’s hydrogen bond structure. Ions in solution can be transported or can take part in reactions. Polar substances which dissolve are hydrophilic and non-polar, which cannot dissolve in water, hydrophobic.
Water is used in photosynthesis, so it is responsible for the production of glucose. This in turn is used in the synthesis of many chemicals.
Water helps in the temperature regulation of many organisms. It enables the cooling down of some organisms. Owing to a high latent heat of vaporisation, large amounts of body heat are needed to evaporate a small quantity of water. Organisms like humans cool down effectively but lose only a small amount of water in doing so.
A relatively high level of heat is needed to raise the temperature of water by a small amount due to its high specific heat capacity. This enables organisms to control their body temperature more effectively.
Water is a solvent for ionic compounds. A number of the essential elements required by organisms are obtained in ionic form, e.g.:
(a) plants absorb nitrate ions (NO3–) and phosphate ions (PO4–) in solution
(b) animals intake sodium ions (Na+) and chloride ions (Cl –).