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 and then cross the road.
Never play near or on the road.
Always give signal with your hand before turning, if riding a bicycle or rickshaw.
Never pick up any unattended articles, if you see any, inform to the nearest police station.
Never take any gifts from the strangers.
Keep patience and always wait for your turn at the bus station. Don't keep out any of your body parts out of the window. Get in and get off from the bus carefully.
Never cross railway track if the gate is closed.
Always go to the parks or any nearby area with your parents.
No left turn No right turn No u turn No Cycles
Zebra crossing No parking No stopping No entry
No horn Railway crossing
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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 the other hand, are the phones that we can carry with us whenever and wherever we go. In this way we can keep in touch with our nearest and dearest one, anytime and from anywhere.
Letter
Now, if you need to communicate with a person who has no land phone or a mobile phone, what will you do?
In this situation we write letters. Letters are one of the oldest means of communication that is, sending and receiving messages. We write and post our letters in post offices. Postman carries these letters to our desired addresses.
Telegram
If we need to send very urgent messages to someone very fast, we use telegram.
E-mails
E-mails are the electronic mails, which are send with the help of internet, through a computer. It is one of the fastest and cheapest mode of communication.
Which one of the followings is a means of transportation?
(a) Fan
(b) Bus
(c) Computer
(d) TV
(e) None of these
Answer: (b)
Explanation
Bus is a means of transportation. Therefore, option (b) is correct and rest of the options is incorrect.
Name the fastest means of transport.
(a) Road transport
(b) Rail transport
(c) Air transport
(d) Water transport
(e) None of these
Answer: (c)
Explanation
By air we can travel long distances with shortest possible time. 
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 of the world have a wide network of concrete roads. Vehicles move smoothly on these roads and carry goods and people from one place to another.
Scooter Bus Car Cycle
Rail Transport
Rail transport is one of the cheaper and comfortable means of transport. For example, train. Many countries of the world have a wide network of railway that is used to carry goods and passengers from one place to another place.
Train
Air Transport
Air transport is the fastest means of transport. But it is also the most expensive means of transport. For example, aeroplane, helicopter, etc. You can cover thousands of kilometres in few hours by aeroplane. This mode of transport is becoming popular day by day.
Helicopter Aeroplane
Water Transport
The water transport is the cheapest means of transport. Most of the goods are transported to various countries by this mode. Water transport is also helpful to move from one parts of a country to another through inland waterways. Ship, boat, etc. are the examples of water transport.
Ship 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.
Formation of Season
Look at the following picture of revolution of the earth around the Sun:
Like other planets, earth also revolves around the Sun in an orbit, which is known as revolution of the earth. Earth completes one round around the sun in 365 days or 1 year. The Earth is divided into two halves by an imaginary line which is called equator.
Look at the following picture that shows the equator of the Earth:
The Earth is tilled on its axis. Its bend portion gets direct heat and light from Sun as compared to the back portion, which receives slanted sun?s rays. The part of hemisphere receiving direct sun's rays have summer. At the same time part of hemisphere receiving slanting rays have winter. Summer has longer days and shorter nights and winter has longer nights and shorter days. When our hemisphere is tilted away from the sun we have winter and the other hemisphere has summer. This cycle is repeated every year. But at all the time of the year suns rays fall directly on the equator. Equator, therefore has same season throughout the year.
The given figure represents of which one of the following?
(a) Seasons formation
(b) Day and night formation
(c) Revolution
(d) Both (b) and (c)
(e) None of these
Answer: (B)
Explanation
During the rotation of the earth on its own axis, the part which receives the light of the sun has day and the opposite part has night. Therefore, option (b) is correct and rest of the options is incorrect.
Which one of the following is responsible for occurrence of season?
(a) Rotation of the earth around its own axis
(b) Revolution of the earth 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 was the first woman to go in to the space.
Neil Armstrong was the first person to set foot on the moon. Edwin Aldrin and Michael Collins were with him.
Look at the following picture, an astronaut walking on the surface of the moon:
Between which two planets, asteroid belt can be found?
(a) Venus and Earth
(b) Mars and earth
(c) Mercury and Venus
(d) Saturn and Uranus
(e) Mars and Jupiter
Answer: (e)
Explanation
There is a wide gap between the orbits of Mars and Jupiter, which is due to the presence of a belt of small rocks and stones. This belt is known as asteroid belt. Therefore, option (e) is correct and rest of the options is incorrect.
Name the first dog which went into space.
(a) Tiger
(b) Meteor
(c) Laika
(d) Comet
(e) All of these
Answer: (c)
Explanation
Laika was the name of the dog that went into space. Therefore, option (c) is correct and rest of the options is incorrect.. 
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 of beauty and love. Venus is very beautiful object in the sky. It is called the evening star. Venus is also the brightest and hottest planet. This is because it has atmosphere containing more amount of carbon dioxide, which traps Sun's heat and doesn't allow it to go back. It can be seen in the sky just after the sun sets.
Look at the following picture of the planet Venus:
Earth
This is the only planet in the solar system that has life on it. Earth looks blue from the space because water covers about ¾th of the planet’s surface. This is the only planet with an atmosphere containing oxygen. Water and oxygen are the essential components for life. Earth like all other planets revolve around the Sun which is called the revolution of the earth. The time duration that the earth takes to complete its one revolution around the Sun is known as year.
Earth also rotates on its own axis, known as rotation. It takes around 24 hours to rotate once on its own axis. Days and nights are formed due to rotation and different seasons occurs due to revolution of the earth around the Sun.
Planets revolve around the Sun, similarly moon of the planets revolves around the planets. Earth has one moon. Like planets, moons are also non luminous object. They glow because they reflects Sun's light.
Earth has strong force of gravity that pulls every objects towards itself. Because of this influence only we sit, stand, eat, or do all kinds of activities, otherwise we all would have been floating in the sky.
The most beautiful object in the night sky as seen from the earth is moon.
Moon is the natural satellite of the earth. Moon revolves around the earth and along with it, moon also revolves around the Sun. Our earth is 80 times bigger than the moon. It is at a distance of about 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 ball of burning gas in the sky is called star. Star is a luminous object that produces light of its own. It is seen as a twinkling and shining object in the sky due to the earth's atmosphere. Sun is also a star that has light of its own.
There are about 10000 billions of stars in the universe. Sun is a medium sized and middle aged star nearest to us. People on the earth worship the Sun as it is the ultimate source of energy. No life could exists on this planet without the light and heat of the Sun.
The temperature on the surface of the Sun is almost 5500°c. Gamma rays, x-rays, UV rays, infrared rays and many harmful rays are released from the Sun.
When moon comes in between the earth and the sun, solar eclipse occurs.
Groups of stars are seen in different parts of the sky forming patterns. These patterns resemble to living or non living creatures. Such group of stars are called constellation. Ursa major resembling the shape of big bear, Ursa minor resembling little bear, Orion resembling hunter. Draco resembling dragon which are seen in the sky. Constellations help astronomer in locating things in the sky during night.
Collection of billions of stars in a particular shape is called galaxy. Milky Way is the name of our galaxy, the galaxy closest to us is andromeda. There are billions of galaxies in the universe.
Astronomy is the branch of science that deals with the studying of space and all heavenly bodies. People who study astronomy are called as astronomer.
Look at the following pictures of constellations in the night sky:
Ursa major Orion Draco
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 water is comparatively hotter, as water gets warm or cool slower than land. Hot air above the sea rises up, and the vacant space is taken over by the cool air from the land. The blowing of air from land to see is called land breeze. Land breeze is comparatively dry.
During winter we see fog all around, this is actually formed when dust particles get mixed up with moist air and they are suspended in the air. Our visibility becomes less in fog. Fog disappears when sun shines.
Certain weather patterns are seen in India due to revolution of the earth around the Sun. Weather varies with the season. Since the earth is tilted on its axis, different parts of the earth get closer to Sun at different time periods. Northern hemisphere lean towards the Sun in April - June hence it is summer in that part. Similarly, in December-January when northern hemisphere is away from the Sun, it is winter there.
Rain
Clouds when loaded with water drops fall as rain.
Summer
The time duration in which northern hemisphere is closer to the Sun summer session comes in. During summer, weather is hot.
Rainy
After summer comes the rainy session. Every year, there is a period of time in which wind blow fast and rain and storms is experienced by us. Heavy blow of wind is dangerous to men and their property.
Autumn
This session comes between the end of the summer and the starting of winter. In this season the atmosphere becomes neither too hot nor too cold. Trees shed their leaves during the 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.
When water gets heated, it is converted into water vapor. This process is called vaporization. The boiling point of water is 100°c.
Evaporation
Water is also changes its state in the form of water vapor from the rivers, ponds, lakes, oceans, due to Sun's heat and results in the formation of clouds. This process is called evaporation.
Evaporation becomes faster in the following conditions:
(A) In sunny days
(B) In windy day
(C) When temperature is more
(D) In less humid air
(E) When surface area is larger
Water evaporates fast in sunshine.
Clothes dry up quickly in windy day.
Rate of evaporation becomes faster at high temperature.
Warmer day temperature is of 40°C.
.
After 4 - 5 hours (Potato chips dry up)
Colder day temperature is of 25°C .
.
After 4 - 5 hours (Potato chips still wet)
Dry air absorbs water vapour fast as compared to humid air. Presence of water vapour make it humid. Humid air has lots of water vapor.
Dry up fastly Dry up slowly
Large surface area allows more water vapour to escape
Space occupied by all three states of water
Ice (solid state) has definite shape and size. Whereas water, if kept in glass, takes the shape of glass and if same water is poured in the bowl, it takes the shape of the bowl. Water, therefore, has no definite shape. It takes the shape of 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, smoke and the unburned particles.
When anything burns gases are produced, which is called smoke. Smoke is lighter, hence it rises up high in the sky. Along with smoke some unburned particles also rises up, called soot. Presence of soot in smoke gives it the black colour. Air contains 78% nitrogen, 21% of oxygen and 1% is contributed by other gases, including carbon dioxide.
Due to the gravity of the earth, gas particles remain in the atmosphere of the earth and do not escape into the space.
If we keep all the components of air in increasing order according to their percentage, which one of the following is correct?
(a) Carbon dioxide. Nitrogen, oxygen
(b) Nitrogen, Oxygen, Carbon dioxide
(c) Carbon dioxide, oxygen, nitrogen
(d) Oxygen, carbon dioxide, nitrogen
(e) None of these
Answer: (c)
Explanation
Nitrogen contributes 78%, oxygen contributes 21%, and carbon dioxide contributes 0.03%. Therefore, option C is correct and rest of the options is incorrect.
The thick blanket of air, which surround the earth, is called
(a) Atmosphere
(b) Biosphere
(c) Hydrosphere
(d) All of these
(e) None of these
Answer: (a)
Explanation
The thick blanket of air which surrounds the earth is called atmosphere. Therefore, option (a) is correct and rest of the options is incorrect.. 
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