PTR SCIENCE
★ AIR
Air is present everywhere around us. It has no colour, smell or taste. Air occupies space. In summer, we feel warm because the air is warm. In winter, air around us is cold. Air is one of the primary elements that makes possible life on the earth.
Air is a mixture of many gases, there are water vapour and small particles of dust. Air forms a thick layer around the earth This layer is called atmosphere. Moving air is called WIND. A gentle movement of wind is called breeze.
A strong movement of wind is called storm. The movement of wind also affects the weather.
★What is air made up of ?
Air is a mixture of different gases. In 1789 lavoisier showed that ari mainly consists of oxygen, Nitrogen and Carbon dioxide.
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| Mixture |
Water vapour, dust particles, smoke are also present in the air.
★ Composition of air.
Air is a mixture of many gases. Nearly 78% of air is nitrogen and 21% oxygen. It also contains small amounts of carbon dioxide, hydrogen, orgon, methane, water vapour, smoke and dust.
Nitrogen gas is very important to all living organism. Animals get it from plants. Plants get nitrogen from soil.
The amount of water vapour present is the air is called humidity. Humidity is high when amount of water vapour is more in air. The sweet from our body surface does not evaporate quickly and so we feel uncomfortable when humidity is high in air.
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| Composition of Atmosphere |
Also, the amount of water vapour in the air depends on the season and the place. For example, places near the sea have with more water vapour as compared to place far away it.
★ Uses of air :---
•All living things need air to breathe.
•Plants need air (carbon dioxide) to make their food.
• Oxygen present in the air helps in burning.
•Moving air helps in drying clothes and wet surfaces.
• Balloons, tyre-tubes and many other toys are filled with air.
•Air filled tubes prevent swimmers from drowning.
•Wind help to run windmills.
•Water vapour in air forms clouds that give us rain.
•Clouds reach different places.
★ Properties of air
(i) Air occupies space.
(ii) Air has weight
(iii) Air exerts pressure in all directions
(vi) Air is needed for burning.
★ Air carries information
Air around us carries information. Without air, the drum beat but you wouldn't hear it. When you speak or clap the air around you vibrates. This vibration reach your ears and your ears turn them into sound.
Air pressure play an important role in our daily life. Many things like syringe, dropper, drinking straw, hand pump and many other things work on the principles of air pressure.
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Moisture