Chemistry Chapter 6 Class 10 Notes

Complete Notes of Chapter No. 14: Atmosphere Class 10 or chemistry chapter 6 class 10 notes by Mr. Tasneem Haider. These computerized notes are very helpful in the preparation of chemistry chapter 6 class 10 notes for students of the 10th class Chemistry and these are according to the paper patterns of all Punjab boards.

• Here are the detailed class 10 chemistry chapter 6 notes to help you prepare for your exams.
• Important Multiple Choice Questions (MCQs) of Chapter No. 14: Atmosphere for Chemistry Urdu Medium 10th Class.
• Important Short Questions of Chapter No. 14: Atmosphere for Chemistry Urdu Medium 10th Class.
•  COMPOSITION OF ATMOSPHERE: Atmosphere is the envelope of different gases around the Earth. It extends continuously from the Earth’s surface outwards without any boundary. About 99% of atmospheric mass lies within 30 kilometres of the surface and 75% lies within the lowest 11 kilometres. Percentage composition of atmosphere by volume.
• LAYERS OF ATMOSPHERE: Atmosphere consists of four spheres (layers) extending from the surface of the Earth upwards. The concentration of the component gases decreases gradually upwards, that results in gradual decrease of pressure. But temperature of the atmosphere does not change in a gradual way. It varies in a complex way. Temperature decreases from 17°C to -58°C regularly in the lowest layer extending upto 12 km. This layer of atmosphere is called troposphere. Above this layer lies the stratosphere that extends upto 50 km. In this layer, temperature rises upto 2°C. Beyond the stratosphere lies the mesosphere, covering upto 85 km. In this region, again temperature decreases down to -93°C. Beyond 85 km lies the thermosphere, in which temperature goes on increasing upwards.
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• Troposphere: The major constituents of troposphere are nitrogen and oxygen gases. These two gases comprise 99 % by volume of the Earth’s atmosphere. Although, concentration of carbon dioxide and water vapours is negligible in atmosphere, yet they play a significant role in maintaining temperature of the atmosphere. Both of these gases allow visible light to pass through but absorb infrared radiations emitted by the Earth’s surface. Therefore, these gases absorb much of the outgoing radiations and warm the atmosphere. As the concentration of gases decreases gradually with the increase of altitude, correspondingly temperature also decreases at a rate of 6°C per kilometre. This is the region where all weathers occur. Almost all aircrafts fly in this region.
• Stratosphere: This region is next to troposphere and extends upto 50 kilometres. In this region, temperature rises gradually upto 2°C. The presence of ozone (due to absorption of radiation) in this region is responsible for the rise of temperature in stratosphere. Within this region, temperature increases as altitude increases, such as lower layer temperature is about -58°C and upper layer is about 2°C. Thus, stratosphere is layered in temperature. Since ozone in the upper layer absorbs high energy ultraviolet radiations from the Sun, it breaks down into monoatomic (O) and diatomic oxygen (O2 ).
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•  POLLUTANTS: A pollutant is a waste material that pollutes air, water or soil. Three factors determine the severity of a pollutant, its chemical nature, concentration and persistence. These pollutants are being created and discharged to the environment by human activities. They make the environment (air, water or soil) harmful to life. So the pollutants are those substances which cause pollution. While contaminants are those substances that make something impure. The harmful substances present in air are called air pollutants. Even a beneficial substance beyond a specific concentration may be harmful. Air pollutants change the weather, badly affect the human health, damage the plants and destroy buildings.
•  Types of Pollutants: Major air pollutants are classified as primary pollutants and secondary pollutants. Primary pollutants are the waste or exhaust products driven out because of combustion of fossil fuels and organic matter. These are oxides of sulphur (SO2 and SO3 ); oxides of carbon (CO2 and CO); oxides of nitrogen (specially nitric oxide NO); hydrocarbon (CH4 ); ammonia and compounds of fluorine. Secondary pollutants are produced by various reactions of primary pollutants. These are sulphuric acid, carbonic acid, nitric acid, hydrofluoric acid, ozone and peroxy acetyl nitrate (PAN).