Acid Rain

What causes acid rain?
Acid rain is caused by smoke and gases that are given off by factories and cars that run on fossil fuels. When these fuels are burned to produce energy, the sulfur that is present in the fuel combines with oxygen and becomes sulfur dioxide; some of the nitrogen in the air becomes nitrogen oxide. These pollutants go into the atmosphere, and become acid.
Acidic particles and vapours are deposited via two processes - wet and dry deposition. Wet deposition is acid rain, the process by which acids with a pH normally below 5.6 are removed from the atmosphere in rain, snow, sleet or hail. Dry deposition takes place when particles such as fly ash, sulphates, nitrates, and gases (such as SO2 and NOx), are deposited on, or absorbed onto, surfaces. The gases can then be converted into acids when they contact water.
You can see in picture what includes pollutant gases which cause acid rain .

What does acid mean?
An acid is a substance with a sour taste that is characterized chemically by the ability to react with a base to form a salt. Acids turn blue litmus paper (also called pH paper) red. Strong acids can burn your skin.

What is pH?
The term pH refers to the free hydrogen ions (electrically charged atoms) in water and is measured on a scale from 0 to 14. Seven is considered neutral and measurements below seven are acidic while those above it are basic or alkaline. Every point on the pH scale represents a tenfold increase over the previous number. Thus, pH 4 is 10 times more acidic than pH 5 and 100 times more so than pH 6. Similarly, pH 9 is 10 times more basic than pH 8 and 100 times more basic than pH 7.

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