Properties of metals

Properties of Metals

T H E M E F O U R :

P E R I O D I C I T Y

C h a p t e r 12

• Describe the general physical properties of metals.
• Describe an alloy and give examples of alloys.
• Identify representations of metals and alloys from diagrams of

structures.

• Place common metals in order of reactivity by reference to

reactions with water, steam and dilute hydrochloric acid.

• Deduce the order of reactivity from a given set of

experimental results.

• Describe the essential conditions for the corrosion (rusting) of

iron.

• Describe with examples, the prevention of rusting using the

barrier method.

Learning Outcomes

Multiple Select

Select the physical properties from the list below.

• electrical conductivity

• heat conductivity

• reaction with acids

• melting and boiling points

• density

Multiple Choice

Which word is used to describe can be stretched to form wires?

• ductile

• malleable

• viscous

• resistance

Multiple Choice

Which word is used to describe can be bent and beaten into different shapes?

• malleable

• unreactive

• brittle

• corrosive

Multiple Select

Most metals have high melting points.

Select the exception ones with low melting points.

• lithium

• calcium

• potassium

• lead

• mercury

Multiple Select

Most metals have high densities.

Select the exception ones with low densities.

• sodium

• magnesium

• iron

• potassium

• silver

Properties of Metals

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12.1 The Importance of Metals

What physical properties of copper
make it useful for use as electrical
circuit wires?

Properties of Metals

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12.1 The Importance of Metals

• Metals are useful because of their properties.
• Metals have both physical and chemical properties.

Properties of Metals

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12.2 Physical Properties of Metals

• Metals have some or all of the following physical

properties:

– Ductile (i.e. can be stretched to form wires)
– Malleable (i.e. can be bent and beaten into different

shapes)

– Good conductors of electricity
– Good conductors of heat
– Shiny (though some are dull on the surface but shiny

underneath)

– High melting and boiling points
– High density

Properties of Metals

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12.2 Physical Properties of Metals

THINK TIME:
Is aluminium a shiny metal? Explain.

Ans:
Aluminium is dull on the surface but shiny
underneath. The dull surface is due to the
formation of aluminium oxide when aluminium
reacts with oxygen in the air.

Properties of Metals

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12.2 Physical Properties of Metals

• There are exceptions to the properties of

metals. Examples:

– Sodium has a low melting point and a low density.
– Mercury has a low melting point, and is a liquid

at room temperature.

Properties of Metals

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12.2 Physical Properties of Metals

The physical properties of
metals are related to the
structure of a metal.

Most metals have high
density because of the close
packing of their atoms.

What happens if you change the structure of a metal?

Properties of Metals

T H E M E F O U R :

P E R I O D I C I T Y

C h a p t e r 12

• Describe the general physical properties of metals.
• Describe an alloy and give examples of alloys.
• Identify representations of metals and alloys from diagrams of

structures.

• Place common metals in order of reactivity by reference to

reactions with water, steam and dilute hydrochloric acid.

• Deduce the order of reactivity from a given set of

experimental results.

• Describe the essential conditions for the corrosion (rusting) of

iron.

• Describe with examples, the prevention of rusting using the

barrier method.

Learning Outcomes

Properties of Metals

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12.2 Physical Properties of Metals

• If we change the structure of a metal, we also

change its properties. This is what happens when a
metal is changed into an alloy.

• An alloy is a mixture of metallic elements.

E.g. bronze is an alloy of copper and tin.

• Some alloys contain non-metallic elements.

Alloys

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12.2 Physical Properties of Metals

• Many pure metals

are too soft and
weak because the
layers of atoms can
slide over each
other very easily.

Alloys

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• The different sizes of atoms disrupt the orderly

layers of atoms and make it difficult for the layers
to slide over each other.

12.2 Physical Properties of Metals

• Thus, alloys are

harder and stronger
than pure metals.

Alloys

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• Some examples of alloys:

– Steel: Fe, C, other elements
– Brass: Cu, Zn
– Coin metals: Cu, Ni

12.2 Physical Properties of Metals

Alloys

THINK TIME:
Will the value of a $1 coin be
less than, equal to or more
than $1? Give a reason.
[analysing, explaining]

ANS: The value of a $1 coin is less
than $1. This is because if the
value of the coin is more than $1,
people would melt the coins and
sell the metal at a higher value.

Multiple Choice

Pure metals are generally hard because the layers of atoms can slide over each other very easily.

• False

• True

Multiple Select

Select the true statements.

• Most metals have low densities.

• Metals are poor conductors of electricity.

• Metals are good conductors of heat.

• Pure metals are soft and malleable.

Dropdown

The ​ ​

Select answer

sizes of atoms disrupt the ​

Select answer

layers of atoms and make it difficult for the ​

Select answer

to slide over each other.

Hence, ​

Select answer

are stronger​ and ​ harder than ​

Select answer

Properties of Metals

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• Metals have the following properties:

– they usually have high densities,
– they are malleable and ductile,
– they conduct electricity, and
– they usually have high melting points.

Properties of Metals

T H E M E F O U R :

P E R I O D I C I T Y

C h a p t e r 12

• Describe the general physical properties of metals.
• Describe an alloy and give examples of alloys.
• Identify representations of metals and alloys from diagrams

of structures.

• Place common metals in order of reactivity by reference to

reactions with water, steam and dilute hydrochloric acid.

• Deduce the order of reactivity from a given set of

experimental results.

• Describe the essential conditions for the corrosion (rusting) of

iron.

• Describe with examples, the prevention of rusting using the

barrier method.

Learning Outcomes

Properties of Metals

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12.3 Chemical Properties of Metals

• Chemical properties describe how substances

react, i.e. how they change into other substances.

• Metals that react vigorously are said to be

reactive metals.

• Metals that do not react are unreactive metals.

THINK TIME:
Copper is used to make water pipes. What does this tell us
about the reactivity of copper with water? [inferring]

ANS: The reactivity of copper with water is very low.

Properties of Metals

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12.3 Chemical Properties of Metals

• Some metals react

vigorously with water
or steam.

Reaction of Metals with Water

• Others do not react at

all.

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12.3 Chemical Properties of Metals

• When a metal does react, hydrogen gas is given off

and the oxide or hydroxide of the metal is formed.

Reaction of Metals with Water

Metal
Reaction with cold

water
Products

Potassium

Sodium

Calcium

Reacts very vigorously

KOH and H2

Reacts vigorously

Reacts readily

NaOH and H2
Ca(OH)2 and H2

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12.3 Chemical Properties of Metals
Reaction of Metals with Water

Metal
Reaction with

cold water
Reaction with steam

Products

Magnesium

-

-

Zinc

Iron

Lead

Copper and
Gold

Very slowly

None

None

None

None

Reacts vigorously

Mg(OH)2 and H2

MgO and H2

Reacts but less vigorously
than magnesium
ZnO and H2

Reacts slowly

Fe3O4 and H2

None

None

None

None

Properties of Metals

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12.3 Chemical Properties of Metals

• Many metals react with dilute hydrochloric acid.
• The products are a metal chloride and hydrogen

gas.

Reaction with Dilute Hydrochloric Acid

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12.3 Chemical Properties of Metals
Reaction with Dilute Hydrochloric Acid

Metal

Reaction with dilute HCl

Products

Potassium

Sodium

Calcium

Magnesium

Zinc

Iron

Lead

Copper & gold

Explodes

KCl and H2

Explodes

NaCl and H2

Reacts very fast

Reacts fast

Reacts moderately fast

Reacts slowly

Reacts very slowly with warm HCl

No reaction

CaCl2 and H2
MgCl2 and H2
ZnCl2 and H2
FeCl2 and H2

THINK TIME: Write the balanced equation for
the reaction of lead with warm HCl.

None

PbCl2 and H2

Properties of Metals

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• Most metals react with water. The reactive metals

can react with cold water.

metal + water metal hydroxide + hydrogen

• The less reactive metals react when heated in

steam.

metal + steam metal oxide + hydrogen

• Most metals react with dilute hydrochloric acid.

metal + hydrochloric acid metal chloride + hydrogen

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12.4 The Reactivity Series

• The reactivity series is the

order in which metals are
listed according to their
chemical reactivity.

Silver is often used for ornaments because of its low
reactivity and attractive appearance.

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12.4 The Reactivity Series

• Aluminium does not appear to

react with water or steam,
suggesting that it is low in the
reactivity series.

• Metal is covered with a thin layer

of aluminium oxide that protects
the metal from reacting.

The Position of Aluminium

Why?

What happens if this oxide layer

is removed?

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12.4 The Reactivity Series
Hydrogen in the Reactivity Series

• Hydrogen can be placed in the

reactivity series.

• Metals below hydrogen in the

series do not react with acids to
produce hydrogen gas.

Where?

This is why copper does not
react with dilute HCl.

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12.4 The Reactivity Series

• The reactivity series is used

in the extraction of metals
and the prevention of
rusting.

Using the Reactivity Series

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12.4 The Reactivity Series

• When metals react with water or dilute

hydrochloric acid, the metal atoms lose electrons
to become ions.

• The more readily a metal gives up electrons to

form ions, the more reactive it is.

• Therefore, the reactivity series is also a measure

of how readily a metal gives up electrons to form
positive ions.

An Explanation for the Metal Reactivity Series

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12.4 The Reactivity Series

• A metal ‘high up’ in the reactivity series:

- reacts vigorously with chemicals,
- readily gives up electrons in reactions to form positive

ions, and

- corrodes easily.

• A metal ‘low down’ in the reactivity series:

- does not react vigorously with chemicals,
- does not readily give up electrons in reactions to form

positive ions, and

- does not corrode easily.

An Explanation for the Reactivity Series

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12.4 The Reactivity Series

• The reactivity of a Group I or Group II metal

increases down the Group.

• Across a period, from right to left, the reactivity

of metals increases.

Reactivity and the Periodic Table

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• The reactivity series compares the reactivity of

metals. Metals ‘high up’ in the series are very
reactive. Metals ‘low down’ in the series are not
very reactive.

• The reactivity series is a measure of how readily

metal atoms give up electrons to form positive
ions. The ‘higher up’ the metal is, the more
readily it forms positive ions.

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12.5 Rusting

• The corrosion of iron and steel is called rusting.
• The brown solid product formed during rusting is

called rust. It is mainly hydrated iron(III) oxide,
Fe2O3.xH2O.

The ‘x’ indicates
that the amount of
water in rust
varies.

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12.5 Rusting

• Air, and
• Water

Conditions for Rusting

A: contains
water but no air

B: contains air
but no water

C: contains both
air and water

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12.5 Rusting
Conditions for Rusting

• Other factors can speed up rusting, such as

dissolved salt.

• For example, iron near the sea rusts faster as

water on the iron surface contains dissolved salt.

+

+

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12.5 Rusting
Conditions for Rusting

THINK TIME:
Explain the following:

1.Little rusting occurs in the Sahara desert.

ANS: The Sahara desert is very dry. Rusting occurs in the presence of
water. The lack of water means little or no rusting.

ANS: Since the air in Singapore is very humid, both water and oxygen are
present so rusting occurs. (The warm temperatures also increase the speed
of rusting.)

ANS: There is no air or water on the moon and so there is no rusting.

[explaining]

2. Iron objects rust easily in Singapore.

3. Iron will not rust on the moon.

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One of the methods used is surface (or barrier)
protection.

12.5 Rusting
Preventing Rusting

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12.5 Rusting

• The surface of an object is

covered with a layer of
substance such as:
−paint (e.g. street poles),

−oil or grease (e.g. machinery),

−plastic (e.g. metal clips), and

−metal plating (e.g. food cans).

• The layer stops the air and

water from reaching the iron
and steel underneath.

Surface Protection

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• Iron and steel rust in the presence of water and

air.

• Rusting can be prevented by coating the object

with a layer of substance. This can be paint, oil,
grease or another metal. It prevents air and
water from reaching the iron.

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