# 2nd Class Science Air, Water and Weather

Air, Water and Weather

Category : 2nd Class

AIR, WATER AND WEATHER

FUNDAMENTAL

• Air is present in the environment. Air is a mixture of different gases like nitrogen, oxygen, carbon dioxide etc.
• Air contains 78% nitrogen, 21% oxygen and remaining 1% other gases.
• Living things need air to breathe. We must breathe in fresh and clean air.
• Wind is the movement of air, there are mainly two types of wind - global wind and local wind.
• Global winds are the dominant prevailing wind patterns that blow in a fairly, constant, steady direction across our earth.
• Local winds are small scale wind of local origin caused by temperature difference. They can move up, down and horizontal. E.g. wind of mountain areas.
• Breeze $\to$ A gentle wind is called breeze. Motion of air from sea to land is called sea breeze and land to sea is called land breeze.
• Storm $\to$ A storm is very bad weather, with heavy rain, strong winds. It includes thunder and lightning. So, storm is a strong wind, it can be dust storm, snow storm, rainstorm etc. e.g. of circular storm is cyclone. It causes damages to trees, houses and other things.
• A very strong wind is called gale.
• All living things need water to live. Life is impossible without water.
• Water, ice and water vapors are three states of water. All the three forms are inter convertible.
• Freezing point of water is $0{}^\circ C$and boiling point of water is$100{}^\circ C$.
• We get water from rain. These are the sources of surface water. The main sources of' water are rivers, lakes, ponds and reservoirs.
• Some rainwater seeps into the ground called ground water.
• Water cycle $\to$ As the Sun heats up the water in river, lakes, ponds and sea, the water vapor rises. Then, it cools and forms small water droplets. Cloud are formed which give rain, which goes back to seas and rivers. This is called water cycle.
• Evaporation $\to$ the change of state from a liquid to a gas is called evaporation.
• Rate of evaporation depends upon temperature, wind, area of exposed surface and humidity.
• Condensation $\to$ the change of state of steam from a gas to a liquid is called condensation.
• Water is very precious. So we should conserve it. Reducing, revising and recycling are the ways of conserving water.
• There are mainly four seasons in a year - summer, winter, autumn and spring.
• Weather of a place is the combined effect of Sun, air, water and clouds.

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