Air

Objectives

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The Students Will be able - To identify the components and uses of air - To develop skills in performing experiments and arriving at conclusions - To clarify the role of oxygen in the process of burning - To realize the significance of air for the survival of plants and animals on earth - To appreciate the need of air in protecting our atmosphere

Summary

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- Air is all around us. - Our earth is surrounded by a huge envelope of air called the atmosphere. - The process of burning of a substance in the presence of oxygen and releasing a large amount of light and heat is called combustion. - Priestley helped us in understanding the presence of oxygen in air that is produced by plants during photosynthesis which can be used by animals for respiration. - Ingenhousz experiment helped us to know the role of sunlight in evolving Oxygen during photosynthesis. - Air contains 78% Nitrogen, 21% Oxygen, 1% of carbon-di-oxide, water vapour, Noble gases, and dust particles. - Composition of air changes slightly from place to place and also from season to season. - In plants, sunlight Carbon-di-oxide +water ------>Food + Oxygen Chlorophyll - In animals, Food+Oxygen-------> C a r b o n - d i - o x i d e + water + Energy - Aquatic plants and animals use oxygen dissolved in water for breathing. - Ozone layer, present in the atmosphere helps in preventing harmful radiations hitting the earth directly.