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.