Unit – 5
Properties of materials
5.1 Metals and non-metals
Metals
Metals are useful materials . We make different objects using different metals .
Different properties of metals .
1. Metals are strong and tough (strong ,hard ) –
they do not shatter (break) When dropped , they hold large weights without
breaking.
 Example : iron is used for bridges it is strong .
 ( Fe – symbol ) 26 th element on the periodic table
2.Metals are shiny
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Gold is used for jewellery, because it is beautiful, shiny and expensive.
Au – symbol , atomic number 79 .
3 . Metals can be bent ( sharply curved ) , metals are malleable – that means they
can be hammered into shape .
Iron , aluminium, copper, silver ,zinc are malleable
4. Metals are ductile ( able to be deformed without losing toughness)
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They can be drawn out into wires .
Copper is ductile
5.metals are sonorous
Metals make a ringing sound like a bell when they are hit .
Copper, bronze , steel , silver are sonorous .
6. Most Metals have high melting points and boiling points
They do not melt easily
7. Metals are good conductors of heat
Steel conducts heat well , which is useful for cooking pans .
8.some metals are magnetic
Iron , steel , nickel , cobalt these elements are magnetic.
9. Metals are good conductors if electricity. This means electric current can flow
through them .
Copper is used for electrical wiring because it conducts electricity well and it’s
flexible .
Points to remember
 Surface of metals become dull after a while
 Big lumps of metals ( metals without shape ) are hard to test for
flexibility
 Bottles and cups make a ringing sound when they are hit , but they
are not made of metal .
Non – metals ( do not have metallic properties .
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Non metals are very useful because of the chemical reaction they have with
other substances
1 . Non metals look dull , they do not reflect light very well and surface is not smooth
.
2 . Solid non metals are brittle ( if you drop them they may shatter )
3.Non metals do not conduct heat energy well ( used to make handles of cooking
pans )
4. Most non metals do not conduct electricity,( some can be used to make coverings
for electric plugs and cables , they are called insulators , this means they do not
conduct her or electricity .
Properties shared by many non-metals
Many non -metals are gases
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Chlorine – used to kill bacteria. For example , it can be dissolved in water and
then added to swimming pools .
Sulfur – sulfur is added to make it hard
Pure oxygen is used in hospitals for people with breathing difficulties
Sillicon is used to make computer chips .
5.2 Comparing metals and non – metals
Metals and non -metals have different properties
Metals
Most are solid at room temperature
These are shiny
They do not shatter
They conduct heat energy well
They conduct electricity
They are malleable
They are ductile
They are sonorous
Non – metals
Many are gases at room temperature
They are dull
They are brittle
They do conduct heat energy well
Most do not conduct electricity
6.3 structure of Earth 🌎
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Outside part of earth is made of rocks and sea water we call this the
external structure of earth.
The parts of the earth that are below the surface , these parts make up the
internal structure
The internal structure is made-up of different layers
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the crust, the mantle, and the core ( inner core and outer core )
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Crust is made up of rocks ( solid rock )
Mantle is made up of molten rock ( rocks in the mantle are melted by
heat , the melted rocks are called magma )
Core is made up of metals
Outer core – liquid ( molten metals iron and nickel )
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Inner core – solid ( solid metals mostly iron and nickel )
1. Explain continental drift.
In 1912 a German scientist Alfred Wenger suggested that , millions of years
ago , all the land was one large continent , and after millions of years ago
the land broke up and drifted apart, this idea is called continental drift.
2. His evidence of idea was that
 Continents have the same type of rock and fit together
 Continents have the same type of fossils fit together
 Continents have the same shape fit together.
( Wegner could not explain how continental drift happened , so not everyone
believed his ideas.)
3.plate tectonic theory is developed in 1960 explained how continental drift
happened
Earths thin outer shell is broken into pieces called tectonic plates ( earth’s
crust is made of large tectonic plates ) these plates fit together like a puzzle ,
but they are not stuck in one place . They are floating on earths mantle ,a really
thick layer of hot flowing rock . The flow of the mantle causes tectonic plates
to move in different directions. This is how continental drift occurs.
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Plates move only 4 cm each year
Some of the plates are under the oceans – oceanic plates
Some of the plates form continents – continental plates
6.4 changes in the Earth
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The places where tectonic plates meet are called plate boundaries
Plates move only 4 cm a year, geological change happens most
frequently at plate boundaries.
Some geological change is very slow , but some is sudden and violent,
such as volcanic eruptions, earthquakes
Plate boundaries at the edge of Pacific ocean , experiences this more
often , this area is often called Pacific ring of fire .
Movement of plates
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One plate may slide underneath other ( one plate sinks below other ) is
called subduction
Plates moving apart – as tectonic plates drift away from each other ←→
They break and crack when the plates are too thin , at that time lava
erupts from the mantle through the cracks in the crust, this causes a
volcano .
Plates sliding past - ↑↓ - the plates are large and heavy , there is a lot of
friction between these plates , this makes the plates stick together, so
the pressure builds up and causes violent movement, this is an
earthquake.
When tectonic plates move together, the rocks crumple( crash ) and
fold upwards - and form mountains
The Himalayas , rocky mountains , and Ural mountains were all formed when
tectonic plates pushed against together
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