Explain the following terms :(a) Sustainable development(b) Nanomaterial(c) Name the gamma isomer of BHC.

Answer:

(a) Sustainable development: Development that meets the needs of the present generation without compromising the ability of future generations to meet their own needs. In chemistry it means designing processes that use renewable raw materials, save energy and produce little or no harmful waste, so that resources and the environment are conserved.

(b) Nanomaterial: A material having at least one dimension (length, breadth or thickness) in the nanoscale range of 1 to 100 nm. Because of the very large surface area to volume ratio, nanomaterials show properties (optical, electrical, mechanical, catalytic) very different from the bulk material, e.g. nano-gold, carbon nanotubes, nano-TiO₂.

(c) The gamma isomer of BHC (benzene hexachloride, C₆H₆Cl₆) is Lindane (gammexane), used as an insecticide.