Environmental chemistry ppt free download

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Department of Chemistry St. Environment is the sum total of physical and biological factors that directly influence the survival , growth , development and reproduction of organisms. The weathered rock particles come from different types of rock and can vary in size.

The amount of humus can vary depending on the plants and animals that lived in the soil. The amount of water in the soil is affected by the type of rock particles. Clay particles are much smaller than sand. A clay soil is heavier and contains more water than a sandy soil which contains lots of room for air.

Soils have different pHs because they are made up of different rocks and so contain different chemicals. The pH of soil affects the availability of nutrients and plants prefer to grow in soils of a certain pH.

For example, strawberries prefer acidic soil and plums prefer alkaline soil. Why do farmers and gardeners need to check soil pH?

Lime is a base called calcium oxide. What effect does lime have on the pH of soil? Alternatively, they can add chemicals that change the soil pH to suit the plants they want to grow. If soil is too acidic, lime calcium oxide is a base that can be added.

The lime neutralizes the acid in the soil and so increases the soil pH. What type of chemical can be added if soil is too alkaline? Rocks change over time due to environmental conditions such as temperature and acid rain. The breakdown of rocks into smaller fragments is called weathering. What are the three types of weathering? Physical weathering due to extremes of temperature which can cause freeze-thaw or onion-skin weathering. Chemical weathering due to chemical reactions between substances in the rock and acidic rainwater.

Biological weathering due to the actions of plants and animals. Normal rainwater has a pH of about 5.

This natural acidity is due to carbon dioxide which dissolves in rainwater and forms carbonic acid, a weak acid. Rainwater with a lower pH than normal is called acid rain.

The burning of fossil fuels in power stations and cars forms pollutants such as sulfur dioxide and nitrogen oxides. These gases dissolve in rainwater to make sulfuric and nitric acids, which are strong acids and so form acid rain. Why is acid rain a serious environmental problem? Rivers, lakes and streams become more acidic so that animals and plants cannot live in them. Soil that becomes more acidic has les nutrients so trees and other plants cannot grow.

Acid rain also damages trees by breaking down the waxy coating of leaves. What can be done to reduce acid rain and its effects? Sulfur dioxide is formed when coal containing sulfur is burned in power stations. This acidic pollutant can be removed from the gases that are released to the atmosphere. Nitrogen oxides are formed when petrol burns in vehicle engines.