Water
Water: An Overview
- Water is a universal solvent and is essential for biological processes due to its unique set of properties.
- Its scientific formula is H2O, consisting of two hydrogen atoms bonded to one oxygen atom by covalent bonds.
- It is a polar molecule with a slight positive charge on the hydrogen atoms and a slight negative charge on the oxygen atom.
Water’s Characteristics
- The polarity of water molecules leads to them being attracted to each other, forming hydrogen bonds. These bonds account for many of water’s unique properties.
- The cohesive nature of water is due to these hydrogen bonds; cohesion leads to high surface tension.
- Water also demonstrates adhesion, the ability to stick to other polar surfaces.
- It has a high specific heat capacity, meaning it can absorb a lot of heat before its temperature rises significantly. This property helps organisms maintain a constant body temperature.
- Its high latent heat of vaporisation also provides a significant cooling effect with a small amount of evaporation, providing a mechanism for thermal regulation.
- As a solvent, water can dissolve many substances, creating an environment where substances can interact.
States of Water in Biological Systems
- Solid water (ice) is less dense than its liquid state due to the formation of a lattice structure as it freezes. This property allows ice to float on water, providing insulation for aquatic life in winter.
- In liquid form, it acts as the medium for metabolic reactions as well as transport for ions and molecules in organisms.
Importance of Water
- Water’s properties make it indispensable in biological systems. It is a reactant in many biochemical reactions, including photosynthesis and hydrolysis.
- It forms the major component of blood in animals and sap in plants, where it acts as a transport medium.
- Its cohesive and adhesive properties help in the ascent of sap in plants.
- In large quantities, such as in oceans and lakes, it forms a stable environment for aquatic organisms.
Tests for Water
- A common test for presence of water is the Cobalt Chloride test. Cobalt chloride paper turns from blue to pink in the presence of water.
- Water can also be detected using the anhydrous copper sulfate test. Anhydrous copper sulfate is white, and turns blue upon contact with water.