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Land pollution

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Land pollution is the degradation of earth’s land surfaces. It is caused as a result of the misuse of land resources by human beings.

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Water pollution is most often accompanied by land pollution because the waste and unwanted substances are together dumped both on land and in water.

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Oil leakage happens when people are careless or make mistakes. This causes the oil tankers to leak oil into the ocean. 

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The sources of oil leakages are:

a.   Ships

b.   Oil wells

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At times, cars leak oil. This oil gets washed away into the water bodies during rainstorms.

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Water pollution is the contamination of water bodies with harmful substances.

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The first image depicts clean water, while the second image depicts pollution.

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Refrigerator, air conditioners and aerosol sprays

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The harmful consequences are:

a.   Skin cancer

b.   Eye diseases

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If the ozone layer gets depleted, then the UV rays will enter the atmosphere.

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ozone layer

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a. Chlorofluorocarbon

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a.         Solar System

b.         orbit

c.          Alpha Centauri

d.         light year

e.         Planets

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Mars

Its orbit is twice than that of the Earth and it has a thin layer of atmosphere.

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The Earth is called the Blue Planet because 70% of its surface is covered with water.

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Mercury is the closest planet to the Sun. It has no proper atmosphere.

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They both do not have light of their own. They shine because they reflect the light from the Sun.

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Alpha Centauri

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The respective paths taken by the planets to revolve around the Sun are their orbits.

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Neptune is the last planet in the solar system. The moving wind on its surface is the fastest.

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a.         Mercury  Venus  Earth   Mars

b.         Jupiter   Saturn   Uranus   Neptune

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Mars: It is known as red planet because of its red rock and soil.

Jupiter: It rotates faster than any other planet.

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Apart from the Sun, planets and the Moon, there are other heavenly bodies like asteroids, comets and meteorites.

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It is loamy soil.

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It is clayey soil.

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It is sandy soil.

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There are four types of soil. They are:

• Sandy soil
• Clayey soil
• Loamy soil
• Gravel soil

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Pumice

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Water and Wind

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Painting, cleaning, writing, hammering and rubbing are some of the activities that are possible due to friction.

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Hint - Glass

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Hint - The surface of a door mat

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The force of friction resists the motion of an object and slows down or stops an object.

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We can reduce friction by using oil, powder and rollers to move or slide over surfaces.

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A type of force that holds back/resists the movement of objects is called friction.

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Cricket players wear shoes with spikes because spikes increase the friction between the ground and shoes and provide better grip for running.

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We prefer trolley bags to pull heavy luggage because the wheels attached with the luggage bag roll on the ground and reduce the friction. This makes it easier to carry the luggage.

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Some of the applications of friction –
1. Walking over a surface without slipping
2. Driving a car over the road surface
3. Writing on a piece of paper
4. Lighting of a matchstick

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The main limitations of the friction are –
1. A deflated tyre makes it difficult to move a vehicle.
2. We have to use more power to pull or push a heavy object over a surface.
3. Due to friction, useful energy in machinery is wasted in the form of heat energy.

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We should use rubber for brake pads of a bicycle because rubber provides better grip to the rider and protects his/her feet from slipping.

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The friction between the tyres and rough surface will experience more friction.

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Answers may vary

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Loud noise makes us feel restless, irritated and angry. Such noise is usually heard from vehicle’s horns, running of heavy machinery, aero planes and loud music from audio systems and television. In some cases it can cause severe headache, high blood pressure and heart diseases.

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Number of beats or vibrations produced by any object in a second can be termed as the frequency of sound. Pitch is auditory sensation caused by the frequency of sound. Pitch can be distinguished as high or low pitch. Humans can hear a selected range of frequency of sound. Other animals such as elephants, dogs, bats can hear wider range of frequency and therefore they have better ability of hearing.

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Vehicle horns, siren of ambulance, police van and fire extinguisher trucks are some of the examples. These sounds alert the other person about an impending emergency which require cooperation from people.

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Dali’s father works with heavy machines which produce lot of noise. This noise is damaging his ears. Dali’s father should avoid working in an area which is so noisy. In case he has to work in a noisy area he should wear protective ear covers which will reduce the entry of loud noise in his ears.

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If loud music is allowed to play till late at night then it will cause disturbance to people living in the nearby areas. Loud noise will not allow them to sleep or relax.

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a.   Sulphur dioxide          b. Carbon dioxide

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The five causes are:

a.   Burning of wood

b.   Burning of coal

c.    Smoke from factories

d.   Vehicles

e.   Cigarettes

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Reduce, Reuse and Recycle

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Always make sure that the intensity of the sound does not disturb anybody.

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One must avoid honking while driving.

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Cloth and paper bags

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Metal

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Eggshells

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Green car

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Carpoling saves time and money. It also reduces air pollution.

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This type of waste can be easily recycled. It can even, be used  to prepare organic manure or natural fertilizers for agriculture.

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Fruit or vegetable peels, garden waste, paper, egg shells, cardboard boxes, human and animal wastes.

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Organic farming is  an excellent way to reduce soil pollution.  In organic farming, natural fertilizers are used in place of chemical ones.

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People can use bicycles to cover short distances instead of using a scooter, bike or car.

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Some alternatives are electric propulsion vehicles, hydrogen cells and solar powered vehicles.

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More than one-fourth of the greenhouse gases are emitted in to the atmosphere through automobiles.

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Biofuels are primarily used for transportation and also for running vehicles used in agriculture, mining, forestry, construction purposes.

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Dark green coloured bins – for disposing organic waste

Red coloured bins – for disposing batteries or other chemical substance

Blue coloured bins – for disposing plastic

Yellow coloured bins – for disposing glass

Grey coloured bins – for disposing metals

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People tend to throw used packets, poly bags, chemicals and other household wastes into the rivers.  We should also stop throwing waste materials in water to keep the water bodies clean and pollution free.

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We should avoid listening to TVs and music system on loud volume. Always make sure that the intensity of the sound does not disturb anybody.

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It is a type of pollution when excessive amount of loud or an unpleasant sound is produced by running vehicles. Industries and public addressing systems such as loudspeakers also contributes in noise pollution. 

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Carpooling is an efficient way of reducing air pollution.

For instance, if four people travel on the same route to work every day and each of them drives his/her own car.  More the number of cars on roads, higher will be the levels of pollution.  

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When meteorite burn completely giving off steam and heat in the atmosphere, they are called as meteors.

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A beam of light covers 9.46 trillion km in a year. It is known as light year.

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The groups of stars forming a pattern in the sky are known as constellation.

Big dipper is an example of constellation.

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Nicolaus Copernicus

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They are pieces of rock that enter the earth's atmosphere but do not burn completely.

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Asteroids are rocks and comets are frozen snowball of dust and gas.

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Uranus

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Halley's Comet

When they come close to the Sun, they heat up and give off steam and gas. This forms a tail like shape.

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The Moon is the Earth's satellite and it is the closest solar body to Earth. It does not have an atmosphere. So temperature ranges from 100 degree Celsius to -173 degree Celsius. Its surface is full of dust and craters.

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a.         VENUS

b.         EARTH

c.          SATURN

d.         MARS

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a.         False

Mercury is the closest planet to the Sun.

b.         True

c.          False

Venus is called the morning and evening star.

d.         True

e.         False

Saturn is the lightest planet with seven shining rings around its middle.

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cow, dog, rabbit, cat etc.

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Cochlea is the internal part of our ear which converts sound vibrations into electrical impulses. These impulses are then transferred to brain where they are processed.

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The ear drum is a thin membrane which vibrates when sound waves touch it. The vibrations of the ear drum are transferred to the hammer, anvil and stirrups bones which transfer the vibrations to cochlea.

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Tina was irritated due to the continuous loud and unpleasant sound made by her brother.

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Farai is trying to produce music by striking on bowls containing different levels of water. This musical instrument is also known as ‘jal tarang’.

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It is a picture of a headphone. We use it generally to listen to music personally. When we do not use a headphone, the music quality is reduced as most of the sound is lost in the surroundings.