Question

Write short notes on
(a.) Greenhouse effect, (b.) Acid rains, (c.) Chlorofluorocarbons, (d.) Electrostatic precipitators, (e.) Ozone depletion

Answer 1

(a) Greenhouse effect: The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs). The absorbed energy warms the atmosphere and the surface of the Earth.

(b) Acid rains: Acid rain, or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic. The SO${}_2$ and NO${}_x$ react with water, oxygen and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials before falling to the ground.

(c) Chlorofluorocarbons: Chlorofluorocarbons (CFCs) are a group of compounds that contain the elements chlorine, fluorine and carbon. At room temperatures, they are usually colourless gases or liquids which evaporate easily. They are generally unreactive and stable, non-toxic and non-flammable. CFCs are also a part of the group of chemicals known as volatile organic compounds.

(d) Electrostatic precipitators: Electrostatic precipitator, also called electrostatic air cleaner, a device that uses an electric charge to remove certain impurities, either solid particles or liquid droplets from air or other gases in smokestacks and other flues. The precipitator functions by applying energy only to the particulate matter being collected, without significantly impeding the flow of gases. Precipitators function by electrostatically charging particles in the gas stream. Precipitators are often deployed with denitrification units that remove nitrogen oxides and scrubbers or other devices that remove sulfur dioxide.

(e) Ozone depletion: Ozone depletion, gradual thinning of Earth’s ozone layer in the upper atmosphere caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities. The thinning is most pronounced in the polar regions, especially over Antarctica. Ozone depletion is a major environmental problem because it increases the amount of ultraviolet (UV) radiation that reaches Earth’s surface, which increases the rate of skin cancer, eye cataracts, and genetic and immune system damage. Depletion of the ozone layer increased the amount of UV radiation reaching Earth’s surface.