All Students Notes

  Question 3: Explain temperature variations in stratosphere and troposphere. Answer. In troposphere, temperature decreases as altitude increases. Air is warmer near earth and cooler at the top. In this layer, the maximum temperature is 17 oC  and minimum temperature is -55 Oc. On average, for every 1 km increase in altitude, the air gets cool down to 6.5 Oc.  On the other hand, in stratosphere, the temperature increases with increase in altitude. Upper  stratosphere is warmer than lower stratosphere due to formation of ozone and release of heat energy. In this layer, the temperature varies from -55 Oc to -5 OC.  Question 4: List components of stratosphere and troposphere. Answer.  Stratosphere Troposphere Question 5: Describe sources of air pollutants Answer. Sources of Air Pollutants Question 6 : Describe acid rain and its effects. Answer:  Question 7: Describe ozone depletion and its effects. Answer. Question 8: ...

Question: What is ozone hole?  Describe ozone formation and ozone depletions with chemical reactions. Answer. Ozone hole The region in the atmosphere where amount of  ozone has been reduced is known as ozone hole.  Ozone Formation Ozone (O 3 ) is important component of stratosphere that protects living things from harmful ultraviolet radiations. Otherwise, these radiations are dangerous to mankind, animals and plants.  In upper atmosphere, ozone molecules absorb UV radiations and undergo breaking and reformation along with release of heat. In the absence of external interference both breaking and formation rates of O 3 are equal. Human activities discharge certain chemicals such chlorofluorocarbons (CFCs) which disturb this natural balance. Ozone Depletion The gradual decrease in thickness of ozone layer in upper atmosphere due to human activities is called ozone depletion. CFCs are used in refrigerators, room air conditioner and aerosol cans. These gases ...

Question: What is acid rain? Describe its formation with suitable chemical equation. How does it affect iron and marble?  Answer. Acid Rain   The rain water having pH less than 5.6 is called acid rain.  Formation   Normal rain water contains C O 2  and has pH of 5.6. However, acid rain is formed when sulphur dioxide and nitrogen oxides from polluted air dissolve in rain water. Sulphur oxides are produced from reaction of oxygen with sulphur discharged from power plants and nitrogen oxides are produced from reaction of oxygen with nitrogen during burning of fossil fuels in automobiles. Nitrogen oxides are also formed under lightening during thunderstorm. Therefore, during thunderstorm, pH of rain water is further reduced to 2.1 due to formation of more sulphuric acid and nitric acid.  Overall following reaction occur during acid rain formation. Effects of Acid Rain Nearly everything is affected by acidic rains. Metals such as iron, marb...

Question: What is global warming? What are effect of global warming on atmosphere? Answer. Global Warming  The rapid increase in temperature of atmosphere due to release of greenhouse gases (carbon dioxide, methane and water vapors) during burning of fossil fuels and deforestation.  As greenhouse gases are increasing day by day in our atmosphere due to combustion of fossil fuels and deforestation at large level. Molecules of these gases have ability to absorb infra-red radiation emitted from earth surface and re-emit back to earth thus increasing the temperature of atmosphere. Thus, process of increasing the temperature of atmosphere due to greenhouse gases is also referred as greenhouse effect. Thus, higher the concentration of greenhouse gases in atmosphere, the greater will be greenhouse effect.  Effects of global warming  The effect of global warming is being felt all over the world. Overall impact of global warming is given as follows.  • The gr...