CBSE Class 9 Science OTBA Guidance issued by CBSE. Revision worksheets, Sample papers, Question banks and easy to learn study notes for all classes and subjects based on CBSE and CCE guidelines. Students and parents can download free a collection of all study material issued by various best schools in India. The study material has been carefully compiled by the best teachers in India. The students should practice the questions database to get better marks in examination. Please refer to other links for free download of high quality study material. Based on CBSE and CCE guidelines. Based on the same pattern as released by CBSE every year. Study material for final/ term/ SA1/ SA2 Examinations conducted by various schools affiliated to Central Board of Secondary Education (CBSE) in India and abroad. CBSE Study material has been compiled to help students preparation which will helps the students to concentrate more in areas which carry more marks.
1. Theme – Clean Air –A shared Concern
Human activities have put water and air in a bad state
Let’s save, freshen and conserve them before it is too late.
Clean air isvital for theexistence and continuance ofall living organisms onearth. Naturally existing mixture of gases in the atmosphere, comprising of mainly Nitrogen, Oxygen, Carbon dioxide and water vapours, provides excellent conditions to support and sustain life. However, this natural composition of air is getting disturbed due to variety of human activities. Human activities related to mainly industry, vehicular emissions, burning of fossil fuels, accidental nuclear emissions etc. contaminate the natural air with undesired components resulting in air pollution. These components, called pollutants, are not only harmful for living organisms but also affect non–living things adversely. The situation is quite alarming, particularly in big industrialized cities. With worldwide trend of shifting of human population to cities and their human desire to lead more comfortable life, the issues and concerns related to availability of clean air for survival are becoming a great challenge for everyone. The present text attempts to help the reader comprehend the situation in a holistic manner, identify the causes and effects of air pollution, examine and analyze the existing status, reflect, debate and generate ideas as to what actions need to be taken at individual, collective or governmental level to meet the emerging challenges.
The Context The atmosphere surrounding the earth is a mixture of many gases which, along with the other conditions, makes it a unique planet for existence of life. Unprecedented urbanisation and development during the past few centuries and many human activities havedisturbed the natural composition of this atmosphere. It is unfortunate that the cost of development is very heavy and is being paid by causing a severe damage to the life support system in the form of clean air. The contamination of air with undesirable gases and particulate matter is called air pollution. The substances which cause pollution are called pollutants. These are either gaseous pollutants like oxides of carbon, sulphur, nitrogen etc. or particulate matter in the form of dust, smoke, fumes or mist. A person living in a city with polluted air is likely to suffer from one or the other breathing problem.
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