Sunday, 9 December 2012

5.3 The Perfect Placement Of The Earth In The Solar System

Planets In The Solar System

1) The nine planets in the Solar System are at different distances from
    the Sun.

2) The Sun gives out heat and light which reach the planets.

3) The inner planets
    (a) Mercury, Venus, Earth and Mars are four planets that are nearest to
         the Sun.
    (b) These planets are made of rocks.
    (c) Each inner planet has an atmosphere.

4) The outer planets
    (a) Jupiter, Saturn, Uranus, Neptune and Pluto are called the outer planets
         or gas glants.
    (b) They are mainly made of gases.

                   Very hot                                                                                                   Very Cold
                                                                    Distance increases
                                                               Temperature decreases


 ~ Nearest to the Sun.
 ~ Its temperature is too high to support


~ Second planet from the Sun and the nearest
   planet to Earth.
~ The hottest planet in the Solar System as a
    large amount of heat is trapped in its atmosphere.


~ Third planet from the Sun.
~ The only planet where there is life.
~ Has air, water and a suitable temperature.


~ A cold planet where almost all its water is
   frozen. No life exists here.
~ Its surface is covered with a thin atmosphere
   of carbon dioxide.
~ Also called the red planet because its surface
   is covered with red dust.


~ The largest planet.
~ All other planets can fit inside it.
~ Made up of gas.
~ Too cold to support life.


~ The second largest planet.
~ The most beautiful planet as it is
   surrounded by three wide rings.
 ~ Made up of gas.
~ Colder than Jupiter and too cold to
   support life.


~ A greenish blue planet because of the
   presence of methane in its atmosphere.
~ Surrounded by narrow rings.
~ Lies on its side as it orbits the Sun.
~ Much colder than Saturn.


~ Surrounded by a faint ring system.
~ Covered with a blue ocean of liquid
~ As cold as Uranus.


~ The smallest planet and furthest from
   the Sun.
~ The coldest of all the planets.

5) The placement of Earth in the Solar System makes it a perfect planet
     to support life. As the third planet from the Sun, it receives enough
     light and heat from the Sun.

 ~ Moderate surface temperature
~ 70% of the Earth's surface is covered
   with water.
~ A layer of atmosphere surrounds the

6) The temperature of the Earth is suitable to support life because it is not too
    hot or too cold.

7) The Earth's surface contains enough water for the survival of living things.

8) The atmosphere of Earth consists of gases in the correct composition to
    support life.
    (a) Oxygen is needed for breathing.
    (b) Carbon dioxide is needed for plants to make food.
    (c) It protects the Earth from harmful rays of the Sun.

9) (a) The other planets either receive too much or too little heat.

    (b) The atmosphere of the other inner planets is too thin and poisonous to
          living things. For example, 95% of the atmosphere on Mars consists of
          carbon dioxide. The atmosphere of the outer planets is also not suitable
          to support life.

    (c) These planets connot support life because they
  • are either too hot or too cold
  • do not have enough air and water
10) If the Earth were much further from the Sun:         
  • The temperature on Earth would drop drastically. It would be very much cloder.
  •  Huge sheets of ice would cover most parts of the Earth.
  • All living things would die.
11) If the Earth were nearer to the Sun:
  • The temperature on Earth would rise and the condition would become hotter.
  • Water on Earth would evaporate. Deserts would be formed.
  • All plants and animals would die because there would be no water.

Friday, 7 December 2012

5.2 The Relative Size and Distance Between The Earth, The Moon anf The Sun

1) The Sun is very huge when compare to the Earth and the Moon.

2) The ratio of their diameters is as follows:

the Sun

the Earth

the Moon

       Ratio of diameter:  400 : 4: 1
  • The Sun is 400 times bigger than the Moon.
  • The Sun is 100 times bigger than the Earth.
  • The Earth is 4 times bigger than the Moon.

3) The ratio of the diameters is only a rough estimate.

4) The actual diameters of the Sun, the Earth and the Moon are as follows:

The Sun
The Earth
The Moon
Diameter (km)
  • The Earth is not round. The diameter from the north pole to the south pole is 12714 km.
  • The diameter at the equator is 12756 km.
  • The ratio of  the diameter of the Sun to the diameter of the Earth is actually about 110 : 1.

The Relative Distance From The Earth To The Sun And From
The Earth To The Moon

1) The following are the distances between the Sun, the Earth and the Moon.

Between the Sun and the Earth
Between the Earth and the Moon
Distance (km)
150 000 000
382 500

2) The relative distance of the Earth to the Sun and of the Earth to the Moon is as follows:

                                   Earth to Sun               :              Earth to Moon

ratio of distance:            400                          :                       1

5.1 The Solar System

The Constituents Of The Solar System
1) The Solar System consists of:
  • the Sun
  • planets
  • natural satellites
  • asteroids
  • meteors
  • comets
2) (a) The Sun is the centre of the Solar System.
    (b) It is a star because it gives out light and heat. It is the only star in
         the Solar System.

    (c) The Sun is the biggest body in the Solar System. It consists af a ball
          of hot gases.

Planets Of The Solar System

1) Planets are bodies in the Solar System that move round the Sun.
    (a) A planet does not give out its own light and heat.

    (b) We can see other planets from Earth because they reflect light
          from the Sun.

2) There are nine planets in the Solar System:
  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune
  • Pluto (Since 24 August 2006, Pluto is classified as a dwarf planet.)
3) Each planet moves in a large oval path called an orbit. It also rotates on its
    own axis.

                                                  The orbit of the Earth round the Sun
  • The planets that are nearer to the Sun take a shorter time to move around the Sun because they have smaller orbits.
  • The planets that are further from the Sun take a longer time to move around the Sun because they have bigger orbits.
  • For example, Mercury takes about 88 days to move around the Sun while Neptune takes about 165 years.
4) When a planet is further away from the Sun, its orbit is bigger. For example,
     the distance between Jupiter and the Sun is longer than the distance between
     the Earth and The Sun.

5) The time taken by the planets to make one complete movement round the Sun
    depends on their distance from the Sun.

 Positions of planets from the Sun

Natural Satellites

1) Some planets have large bodies that orbit around them. These bodies are
    called natural satellites.

2) The Moon is the only natural satellites of thw Earth. It is smaller than the
    Earth. It orbits round the Earth and the Sun.

3) Mercury and Venus do not have their own natural satellites. Some planets
    have more than one natural satellites.

4) Natural satellites do not give off light or heat. They reflect light from the
    Sun and can be seen from Earth.


1) Asteroids are bodies made up of metals and rocks.

2) Most asteroids are found in the asteroid belt between the orbits of Mars
    and Jupiter.

3) More than 10000 asteroids and more are discovered every month. Ceres
    is the first asteroid to be discovered. It is the largest asteroid.

4) Some asteroids come near the orbit of the Earth. Someday, one of these
    asteroids could hit the Earth.

5) An asteroid hit Earth 65 million years ago in Mexico.



1) A meteoroid is a piece of rock or metal that floats in space.
    (a) Meteoroids come in many shapes and sizes but most of them are small.
    (b) There are millions of meteoroid in space.

2) When a meteoroid enters the atmosphere of the Earth, the friction between
     the meteoroid and the air causes it to glow and give off light. It is called a


3) A meteor looks like a streak of bright light that is seen across the night sky.
    It is also commonly called a shooting star.

4) (a) A meteor that has landed on the surface of the Earth is called a meteorite.
     (b) When a meteorite hits the Earth, a crater or a hole is formed in the ground.

                                                       A crater formed by a meteorite


1) A comet is a lump of ice which consists of frozen gases and dust.

2) Comets move around the Sun in long orbits. They take years to complete
    one orbit.

3) Most comets spend their time beyond the Solar System. When they enter
    the Solar System and come near the Sun, they can be seen from Earth.

4) When a comet comes near the Sun, the heat of the Sun causes the ice at its
    centre to melt. This causes the comet to glow and a long tail of gas and dust
    is visible.

5) The most famous comet is Halley's Comet.

                                                                 A Halley's Comet

Wednesday, 5 December 2012

Video - Make a toy car out of a plastic bottle | recycle | re-use | Africa

Video - Reduce Reuse Recycle Campaign

4.6 Reuse, Reduce and Recycle

Conserving Materials

1) We get natural materials from animals, plants and rocks on the Earth.
     There is a limit to Earth's resources.

2) Some materials are renewable. For example, we grow trees to obtain
    wood and breed silkworms to obtain silk. However, this needs a lot of
    time, effort and money.

3) Non- renewable materials such as petroleum, coal, natural gas and
     metals cannot be obtained once they are used up. They can only be
     obtained from the earth.

4) Altough man-made materials are not obtained directly from nature,
    they are often produced from natural materials such as petroleum.

5) Natural materials and man-made materials are limited. They will be
    used up if there is no effort to conserve them.

6) As such, we should conserve materials so that they would not be used
    up easily.

7) We can help to conserve materials by reusing, reducing and recycling
the things we use every day.

Reusing Materials

1) Reusing is an attempt to use thrown-away materials again for other

2) Instead of throwing things away, we can modify them so that they can
    be used again.

3) This can help to reduce the amount of waste and save a lot of precious

4) Here are some of the things that we can reuse.
    (a) Old newspapers can be used to wrap things. Old magazines and boxes
         can be used to wrap presents.

    (b) Pieces of old cloth can be used to wash cars or to mop floors.


Old tyres are used to decorate gardens.


Reducing The Use Of Materials

1) In order to conserve materials, we must reduce the use of natural materials.

2) Reducing the use of materials can help save production costs and reduce
    the amount of waste.

3) Paper comes from trees. If we use a lot of paper, we need to cut down many
     trees. Using less paper means saving trees. For example,
     (a) write or print on both sides of a paper

     (b) use handkerchiefs instead of tissue paper

4) Use baskets and food containers instead of plastic bags when shopping.

5) Avoid using disposable objects such as plastic spoons and forks,
    polystyrene plates and cups, and wooden chopsticks.

wooden chopsticks

tissue paper

plastic spoon and fork


polystyrene container


Recycling Materials

1) Recycling materials is converting used and old materials into new products.

2) Materials that can be recycled are sent to collection centres for recyclable
     materials or put into recycling bins.

3) The materials are then separated and put into  different bins. These bins are
    marked with recyclable symbols.

4) Materials that can be recycled are glass, paper, aluminium and plastic.

Recycling bins
Brown - glass
Blue - paper
Orange - plastic and aluminium

Friday, 30 November 2012

4.5 Transparent, Translucent and Opaque Materials

1) Depending on whether light can pass through them, materials can be
    classified into 3 groups:
    (a) Transparent materials
    (b) Translucent materials
    (c) Opaque materials

2) Transparent materials allow the most light to pass through.
    (a) Transparent materials can be made of clear glass or clear
    (b) Objects behind a transparent material can be seen clearly.
    (c) Examples: glass, bottle, transparency sheet, light bulb, thermometer,
         beaker, ice, spectacles.

                      Windsreen                                                                   Aquarium

3) Translucent materials allow only some light to pass through.
    (a) Examples of translucent materials are tracing paper, frosted glass
          and certain types of plastic and thin cloth.
    (b) Objects behind a translucent material cannot be seen clearly and
          appeared blurred.
    (c) Othe examples: coloured glass bottle, window pane, plastic bag,
          plastic container.
                                       Frosted glass                                      Lampshade

4) Opaque materials do not allow any light to pass through.
    (a) A shadow forms behind an opaque material when a light shines
         on it.
    (b) Objects behind an opaque material cannot be seen at all.
    (c) Wood, rubber, metals, some plastics and cloth are opaque materials.
    (d) Examples: wall, hat, clothes, towel, box, paper, bag, book.

                              Umbrella                                                   Wooden door

Thursday, 29 November 2012

4.4 Conductors and Insulators

Conductors and Insulators Of Electricity

1) Materials that conduct electricity are called conductors of electricity.

2) Metals such as copper, aluminium, iron, steel and zinc are good
    conductors of electricity.

A iron paper clip is made of iron. The bulb
lights up because electricity flows through
the circuit. Iron is a conductors of electricity.

The wires are made of copper, a good
 conductor of electricity.

3) Materials that do not conduct electricity are called insulators.

4) Plastic materials, wood, rubber, leather, glass and cloth are insulators.

                                      The material covering the wires is an insulator.
                                      Electricity cannot flow through it.

Conductors and Insulators Of Heat

1) Metals are also good heat conductors.

2) A good conductor of heat is also a good conductor of electricity.

3) Materials that do not conduct heat are called heat insulators.

4) Plastic materials, wood, glass, laether, rubber and cloth are also good
    heat insulators.

                       Cooking utensils and electric appliances are made from
                       metals such as iron and steel because they are good
                       heat conductors.

                                Handles of woks and ladles are made from plastic
                                or wood because they are good heat insulators. Users
                                can then hold the utensils without being burned.

4.3 Properties Of Materials

1) Different materials have different properties or characteristics as follows:
  • conduct electricity
  • conduct heat
  • float in water
  • absorb water
  • can be stretched
  • allow light to pass through
2) Materials that conduct electicity
    (a) A material that allows electricity to pass through it conducts electricity.
    (b) Objects made of metals, such as copper, iron and steel, can conduct
         electricty. Wires are made of copper (a metal) which can conduct electricity.
    (c) Carbon is a non-metal that can conduct electricity. Other non-metals
          cannot conduct electricity.

3) Materials that conduct heat
    (a) Materials that allow heat to flow from one part of an object to another
         conduct heat.
    (b) Objects made of metals can conduct heat easily. Metals such as steel and
          aluminium are used as cooking utensils to conduct heat quickly.
    (c) Non-metals, such as wood, rubber, leather, glass and plastic, do not conduct
        heat and electricity.
    (d) Materials that conduct heat can also conduct electricity.

The bulbs light up because the wires conduct electricity.
The pan conducts heat to the food quickly.
4) Materials that float in water
    (a) Objects that are made of wood and plastic can float in water.
    (b) They do not sink when put in water.
    (c) Objects made of glass, metal, cloth and clay sink in water.

Objects that float or
sink in water.

5) Materials that absorb water
    (a) Materials such as wood and cloth absorb water.
    (b) Objects such as a tissue and a towel become wet when they come
         into contact with water. These objects can be used to wipe wet surfaces.
    (c) Objects made of glass, metal, clay, rubber and plastic cannot absorb water.
         Water droplets can be seen on their surfaces when they come into contact
         with water.
    (d) Materials that do not absorb water are used to make waterproof objects
          such as umbrelas, raincoats and tents. These objects stop us from getting

6) Materials that can be stretched
    (a) Objects made of rubber can be pulled and stretched.
    (b) These objects retutn to its original shape and size when released. They are
    (c) Examples of objects that can be stretched are rubber bands and springs.

A rubber band can be stretched.

7) Materials that allow light to pass through
    (a) Glass and certain types of plastics allow light to pass through them. An
          object can be seen if placed behind such materials.
    (b) Wood, metal and rubber do not allow light to pass through them. Objects
          cannot be seen if placed behind them.

Wednesday, 28 November 2012

4.2 Classification Of Materials

1) Some objects are made of one type of material. For example, a towel is made from cloth.

2) Some objects are made of more than one material.

3) An object can be made from different materials. For example, a mug can be made of glass, clay, plastic or stainless steel.

4) A material can be used to make different objects. For example, plastic can be used to make waste-paper baskets, containers, pencil boxes and cup.

Test Youself

Fill in the blanks with the correct words.


1) We uses a _____________ of materials to make many types of objects.

2) Objects can be made from rubber, plastic, metal, _____________ or _____________.

3) Objects can be grouped according to the ____________ they are mede of.

4) Nails, needles, screws and knives are objects that are made of ____________.

5) Erasers, car tyres and balloons are objects that are made of ___________.

4.1 Materials Around Us

1) There is a great variety of materials around us.

2) The following materials can be used to make different objects.


 Objects: furniture, blackboard, boat, ruler, pencil, paper, book.


Objects: spoon, knife, scissors, nail, ring, necklace, pot, pan, coin, tin.


Objects: jug, glass, mirror, window pane, bottle.


Objects: eraser, hose, gloves, boots, tyre, ball, balloon, rubber band.


Objects: curtain, towel, clothes, handkerchief.


 Objects: belt, hat, shoes, wallet, handbag.

 Objects: ruler, bottle, containers, waste-paper basket, toothbrush, comb.

 Objects: vase, ceramic tile, brick, bowl, plate, flower pot.