3rd Class

     Safety   Life is very precious to all of us. But at times we may endanger our lives by accident. Accident is an undesirable phenomena and it may occurs anywhere, anytime. Sometimes two vehicles may collide with each other, someone get burn, some may be bitten by dogs, cats and insects etc. These accidents occur by chance. But many times, accidents occur because of our negligence. Such accidents can be prevented by following certain safety rules, outside and inside our houses.             Safety Measures to be Followed Outside the House Always follow the traffic rules while moving on the road. Always walk to the left side of the road. If there is pavement, walk on it. Always cross the road at the zebra crossing to avoid accidents. First look to the right and left more...

     Communication   We use various means of transport to meet our friends and relatives. But sometimes we are not in a position to visit and meet them. In that case, means of communication helps us to keep contact with them, by sending and receiving messages.            Means of Communication There are various means of communication. These are:             Telephone Telephones are land phones used for communication. By telephone we can talk to the persons living far away from us. We can even talk if the person is in another part of the world.            Mobile phone We cannot carry our land phones with us whenever we go out of our house. Mobile phones/ cell phones, on more...

     Transport   Transport is the movement of people and goods from one place to another. It is performed by various modes such as road, rail, air, water, etc.          Means of Transport Mode of transport is divided into three categories. (i) Land transport (ii) Air transport (iii) Water transport            Land Transport Land transport is the most common and one of the oldest means of transport. In this mode, transportation is done by road and rail. Thus, the two types of land transports are road transport and rail transport.              Road Transport Road transport is the transport on road for passengers and goods. For example, cart, bicycle, rickshaw, car, scooter, bus, etc. Most of the countries more...

       Formation of Day and Night   Look at the following picture that shows the formation of day and night:   The earth not only moves around the Sun in an orbit, but also rotates on its own axis. This is known as rotation. Many countries are there on this planet. Part of the earth which faces Sun during rotation has day, while the portion on the back side is in dark and has night at that time. After few hours, the illuminated part turn away from Sun and has night, while the dark portion becomes illuminated with sun's light and has day. This cycle repeats. Every part has both day and night in 24 hours. The Earth rotates from west to east, hence the Sun appears to rise from east and sets in west. more...

     Other Heavenly Bodies   Minor planets in the solar system that are made up of rocks is known as asteroid. These are found circling between Mars and Jupiter.              Meteors It is also known as shooting star, made up of rock and metal. This is formed when meteoroid enters the earth's atmosphere and burns up. It is seen as a streak of light in the sky.   Look at the following picture of Meteors:              Some interesting Points about the Space Exploration Yuri Gagarin from Russia was the first person to go into the space, in Vostok 1. Laika a dog was the first living organism to go into the space. Valentine Tereshkova from Russia more...

     Planets   There are eight planets, which revolve around the Sun. Mercury, Venus, earth, and Mars are called inner planets, as they are very close to the Sun. Jupiter, Saturn, Uranus and Neptune are called outer planets as they are far away from the Sun.            Mercury Mercury is the smallest planet in the solar system. It looks like our moon. The surface of mercury is covered with craters. Though it is nearest to the Sun, but it is less hottest than Venus. The reason is that the mercury has no atmosphere to retain Sun's heat on it.   Look at the following picture of the Mercury:                Venus Venus is named after roman goddess more...

     Our Universe   Everything which we see in the sky, that is stars, moons, planets, comets, even the earth on which we are living and all other heavenly bodies make our universe. In this chapter we will study in brief about the important components of universe.              Solar System Solar system is having Sun at the center and all the other eight planets with their moons. All these and also the smaller objects like comets, asteroids meteorites etc. revolves around the Sun. These celestial bodies don't fly away as the strong force of gravity of the sun continuously pull them towards itself.   Look at the following picture of our solar system:              Star Big more...

     Weather   Weather of a place is the combined effect of Sun, wind and water. Sun plays an important role in changing weather. At noon sun's rays fall directly over our head and hence it is the hottest time of the day. Morning and evening are comparatively less hotter because rays fall at an angle. Land gets heated faster and also cools down faster than water.   During the day time land gets heated faster. Therefore, air near the land becomes hot, hot air goes high up and, cool air from the sea comes to take its place. This blowing of air from sea to land is called sea breeze and it flows during the day time. Sea breeze is cool and pleasant. During the night, when there is no sun rays, land gets cooled faster. Sea more...

     Water and its Different States   Water is a wonderful liquid that dissolves many substances in it. Life is impossible without water.             Different States of Water Water, ice, and water vapours are three states of water. All the three forms are interconvertible.   Look at the following picture of the changes of water, from one state to another:                Inter conversion of different states of water One state of water can be converted into another either by gaining energy or by releasing.                                      Freezing is changing the state of water into ice. It occurs at 0°c.   more...

   Air   Every empty space is filled with a mixture of gases, called air. Gasses present in air are nitrogen, carbon dioxide, oxygen, helium, argon and many more.            Importance of Air Air is essential for existence of life. Without air life cannot survive. We breathe in oxygen, without which we can't live even for a minute. Not only humans, all kinds of life, that is, cats, dogs, microorganisms, birds, snakes, lizards, frogs or even plants need oxygen to survive.   Look at the following picture of burning of wood which require oxygen:   Everything burns only in the presence of oxygen. Air becomes thinner and thinner, as we go up higher and higher. Therefore, astronauts and mountaineers carry oxygen cylinder with them. Air also consists of water vapor, more...