air around us pure. class 6

Air around us

Atmosphere: The envelope of air that surrounds the earth is known as the atmosphere. The atmosphere of Earth is the layer of gases, known collectively as air. Earth's atmosphere stretches from the surface of the planet up to as far as 10,000 kilometres (6,214 miles) above

·         The air becomes thinner and thinner as we go high up from the surface of the earth.

·         The atmosphere is quite active due to the movement of air, with respect to the earth.

·         The processes like cloud formation, thundering, rain etc., occur in the atmosphere. Uses of Air

Wind: When air is in motion, it is called wind.

Weathercock: It shows the direction in which the air is moving at that place.

Air: Air is a mixture of different gases. Air is also present in things which seem to be empty.

Properties of air

·         It is colourless i.e., it has no colour and taste.

·         It is transparent i.e., we can see through it.

·         Air occupies space. It fills all the space in a container which is otherwise empty and seems to be empty.

·         Air exerts pressure in all directions.

All living organisms require air for their survival because it contains O₂ (oxygen gas) and CO₂ (carbon dioxide gas) as parts of its mixture.

Uses of Air

·         Air exerts force on objects that come in its way. This property of air is quite useful.

·         Fun like firkins, pinwheel is based on the force applied by air.

·         The air current makes the windmills to rotate.

• Air helps in the movements of sailing yachts, sliders, parachutes and aircraft.
• Air also helps in dispersal of seeds and pollens of flowers.
• Compressed air is used in tyres of vehicles.
• Nitrogen is used on a large scale to manufacture fertilizers.
• Winnowing is possible only because of the air.
• Air is also useful for playing several musical instruments.
• Birds, bats and many insects fly in the air.
• We cannot hear the sounds in the absence of air.
• Various components of airplay various important roles.

Composition of Air

·         Air is not one substance but is a mixture.

·         Air is a mixture of some gases, water vapour and dust particles.

·         The gases in the air are mainly nitrogen, oxygen, a small amount of carbon dioxide and some other gases.

Water vapours

·         Air contains water vapours.

·         When air comes in contact with a cool surface, it gets cooled and fog appears.

·         The presence of water vapour in the air is important for the water cycle in nature.

Dust particles

·         Air contains dust particles.

·         The presence of dust particles in air varies from place to place and time to time.

Smoke: These are the dark-coloured gases caused by burning of anything.

Oxygen

·         The component of air that supports burning is called oxygen.

·         Oxygen is necessary for the survival of all living beings. It is required in respiration.

·         Percentage of oxygen in the air is around 20.95%.

Nitrogen

·         The major part of the air is nitrogen. It takes up four-fifth of the space (be around 78.11%) that air fills.

·         Nitrogen does not support burning.

Carbon dioxide

·         Carbon dioxide makes up a small component (0.03%) of air around us.

·         It causes a feeling of suffocation.

·         All materials, when they burn consume oxygen and produce carbon dioxide.

·         It is also produced along with water vapour during respiration.

·         Plants need carbon dioxide for photosynthesis and to live.

Oxygen Cycle: The oxygen cycle is the biogeochemical cycle of oxygen. It is mainly involved in maintaining the level of oxygen in the atmosphere. 

 

• Step 1: In the first step plants are included. Plants give out oxygen during the process of photosynthesis.
• Step 2: Animals and other aerobic organisms take in oxygen to respire.
• Step 3: These living beings release carbon dioxide into the atmosphere during the process of respiration. This carbon dioxide is again used by plants for photosynthesis to produce oxygen.

 

Air Supports Life
We all need air to survive. Air contains oxygen and carbon dioxide useful to plants and animals. Plants use carbon dioxide of the air to make their own food by a process called photosynthesis. Let us see how air supports life in plants and animals.

In Plants:
Plants have tiny pores called stomata, found on the underside of a leaf . Air containing carbon dioxide and oxygen enters the plant through these openings where it gets used in photosynthesis and respiration.

In Animals:
All animals need to respire, be it a cockroach, a fish, or an elephant. It is just that they use different organs and mechanisms for respiration.

In Aquatic Animals and Plants:

Most aquatic animals like fish, tadpole, crab, and shrimp have special organs for respiration called gills. Gills help to take in oxygen and give out carbon dioxide. Some aquatic animals like dolphin and whale come to the surface of the water regularly to take in air, since they breathe with the help of the lungs.

Aquatic plants like Hydrilla also breathe in oxygen dissolved in water through their stomata.

Balance Of Oxygen And Carbon Dioxide In The Air

The balance of oxygen and carbon dioxide in the atmosphere is maintained through respiration in plants and animals and by photosynthesis in plants. Plants produce oxygen during photosynthesis and utilize oxygen during respiration. They produce much more oxygen during photosynthesis than they consume, during respiration This is how the oxygen consumed by plants and to a large extent by animals is replenished in the air through photosynthesis.

 

Water cycle
The cyclic movement of water from the atmosphere to the Earth and back to the atmosphere through various processes is called as water cycle.
Different steps of water cycle include evaporation, transpiration, condensation, precipitation and surface run-off.

a) Evaporation - The water present on the surface of oceans evaporates by the sun’s heat. This process of conversion of water from liquid state to vapour state is called evaporation. Evaporation also takes place from wet clothes, fields, ponds, lakes and rivers.

b)Transpiration - Plants take in water from the soil to prepare their own food and also for other life processes. They release excess water into air in the form of water vapour by the process of transpiration.

c) Condensation - The evaporated water is carried away by warm air. As the warm air moves higher from the surface of the Earth, it starts to cool down. This water vapour condenses to form tiny water droplets which float in air to form clouds or fog.

d) Precipitation - All these droplets collect to form bigger drops of water. Bigger water drops come down ads rain by the process of precipitation. If the air is too cold, the water drops can become snow or hail and may settle on the top of a mountain. When these snow or hail melts, they can become part of a river or a stream.

e) Surface run-off – Some amount of rain water is absorbed by the soil and settles down as ground water. Most of the rain water flows down the hills and mountains to collect into rivers, lakes or streams. Rain also washes away the topmost layer of the soil into water bodies.

This circulation of water through all these different factors is called as water cycle.