Q.(a) What are the various essential properties of water ? OR

(a) Water's solvent power, thermal stability and cohesive properties made the primitive oceans the medium in which life's building blocks could form and interact. (b) The main menstrual disorders are amenorrhoea, dysmenorrhoea, menorrhagia, oligomenorrhoea, and PMS.

(a) In theories of the chemical origin of life (chemogeny), water is considered essential because of several of its physico-chemical properties. As an excellent, near-universal solvent, water can dissolve a very wide range of inorganic salts and organic molecules, bringing them into close proximity so they can react and combine into progressively more complex molecules. Its unusually high specific heat capacity and high latent heat of vaporisation allowed the primitive oceans to absorb and buffer large amounts of solar and volcanic heat without extreme or rapid temperature swings, providing a relatively stable environment for slow, sustained chemical reactions. Water's high surface tension and strong cohesive/adhesive forces (from hydrogen bonding) helped hold molecules together and could have assisted in concentrating organic molecules at interfaces (such as around clay particles or in coacervate droplets), a step believed important for the formation of the first protobionts/pre-cells. Water also remains liquid over a wide temperature range and is denser as a liquid than as ice, so large, stable bodies of liquid water (oceans) could form and persist on the early Earth, offering the arena in which the classic Oparin-Haldane/Miller-Urey model of chemical evolution is thought to have taken place. …