Thursday, 13 December 2012
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
Mercury
~ Nearest to the Sun.
~ Its temperature is too high to support
life.
Venus
~ 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.
Earth
~ Third planet from the Sun.
~ The only planet where there is life.
~ Has air, water and a suitable temperature.
Mars
~ 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.
Jupiter
~ The largest planet.
~ All other planets can fit inside it.
~ Made up of gas.
~ Too cold to support life.
Saturn
~ 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.
Uranus
~ 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.
Neptune
~ Surrounded by a faint ring system.
~ Covered with a blue ocean of liquid
methane.
~ As cold as Uranus.
Pluto
~ 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
Earth
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
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.
Distance increases
Temperature decreases
Mercury
~ Nearest to the Sun.
~ Its temperature is too high to support
life.
Venus
~ 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.
Earth
~ Third planet from the Sun.
~ The only planet where there is life.
~ Has air, water and a suitable temperature.
Mars
~ 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.
Jupiter
~ The largest planet.
~ All other planets can fit inside it.
~ Made up of gas.
~ Too cold to support life.
Saturn
~ 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.
Uranus
~ 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.
Neptune
~ Surrounded by a faint ring system.
~ Covered with a blue ocean of liquid
methane.
~ As cold as Uranus.
Pluto
~ 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
Earth
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
- 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.
- 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
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 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.
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
Approximate
ratio of distance: 400 : 1
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)
|
1391016
|
12756
|
3480
|
- 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.
Distance
|
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
Approximate
ratio of distance: 400 : 1
5.1 The Solar System
The Constituents Of The Solar System
1) The Solar System consists of:
(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:
own axis.
The orbit of the Earth round the Sun
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.
Asteroids
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.
Asteroids
Meteors
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
meteor.
Meteor
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
Comets
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
1) The Solar System consists of:
- the Sun
- planets
- natural satellites
- asteroids
- meteors
- comets
(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.)
own axis.
- 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.
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.
Asteroids
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.
Meteors
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
meteor.
Meteor
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.
Comets
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.
Wednesday, 5 December 2012
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
purposes.
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
materials.
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
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
purposes.
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
materials.
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
plastic.
(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
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
plastic.
(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.
__________________________________________________________________
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.
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.
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:
(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.
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
wet.
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
elastic.
(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.
- conduct electricity
- conduct heat
- float in water
- absorb water
- can be stretched
- allow light to pass through
(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.
(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
wet.
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
elastic.
(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 ___________.
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.
rubber
|
materials
|
metals
|
variety
|
wood
|
glass
|
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.
_____________________________________________________________________
Wood
Objects: furniture, blackboard, boat, ruler, pencil, paper, book.
____________________________________________________________________
Metal
Objects: spoon, knife, scissors, nail, ring, necklace, pot, pan, coin, tin.
________________________________________________________________________
Glass
Objects: jug, glass, mirror, window pane, bottle.
________________________________________________________________________
Rubber
Objects: eraser, hose, gloves, boots, tyre, ball, balloon, rubber band.
_________________________________________________________________________
Cloth
Objects: curtain, towel, clothes, handkerchief.
________________________________________________________________________
Leather
Objects: belt, hat, shoes, wallet, handbag.
________________________________________________________________________
Plastic
Objects: ruler, bottle, containers, waste-paper basket, toothbrush, comb.
________________________________________________________________________
Clay
Objects: vase, ceramic tile, brick, bowl, plate, flower pot.
_______________________________________________________________________
2) The following materials can be used to make different objects.
_____________________________________________________________________
Wood
____________________________________________________________________
Metal
Objects: spoon, knife, scissors, nail, ring, necklace, pot, pan, coin, tin.
________________________________________________________________________
Glass
Objects: jug, glass, mirror, window pane, bottle.
________________________________________________________________________
Rubber
Objects: eraser, hose, gloves, boots, tyre, ball, balloon, rubber band.
_________________________________________________________________________
Cloth
________________________________________________________________________
Leather
________________________________________________________________________
Plastic
________________________________________________________________________
Clay
_______________________________________________________________________
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