C19 metals and their reactivity

 Describe the physical and chemical properties of
metals;
 Explain why metal alloys are often used in place of
metals;
 Discuss the reactivity of metals, and deduce the order
of reactivity of metals based on experimental results
of data supplied
 Describe the reactions of metallic hydroxides, nitrates
and carbonates
LEARNING OUTCOMES
Metals and Their Reactivity
Chapter 19

Physical Properties of metals
 Metals are usually hard and shiny.
 They are malleable (can be bent or hammered
into sheets) and ductile (can be stretched or
drawn into wires).
 Pure metals are weak because their atoms can
slide over each other easily when a force is
applied.
Chapter 19

Physical Properties of metals
 Metals are good conductors of heat and electricity.
 Metals have high density.
 They have high melting points and boiling points.
E.g. iron has a melting point of 1538 o
C and
tungsten has a melting point of 3422 o
C.
Chapter 19

Chemical Properties of metals
 Metals lose electrons to form positively charged ions
(electropositive).
Cu  Cu2+
+ 2e−
 Most metals react with acids to produce hydrogen gas.
Mg(s) + H2SO4(aq)  MgSO4(aq) + H2(g)
 Metals form basic oxides when they react with oxygen.
2Ca(s) + O2(g)  2CaO(s)
 Most metals react with water to produce metallic hydroxides
and hydrogen gas.
2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)
Chapter 19

Structure of metals
 The atoms of metals are packed
very closely together in neat layers.
 Pure metals are weak
because the layers of atoms
can slide over one another
when a force is applied.
Chapter 19

Alloys of metals
 A mixture of a metal with
another metal (or non-metal) is
called an alloy.
Brass
BronzeBronze
Stainless steel
 Brass is an alloy of copper and
zinc; bronze is an alloy of copper
and tin.
 Stainless steel is an alloy of iron
and small amounts of carbon,
chromium and nickel.
Chapter 19

Structure of alloys
 In alloys, the atoms of different
metals or elements are of
different sizes.
 This disrupts the orderly layers
of atoms and makes it harder
for the layers of atoms to slide
over one another when a force
is applied.
 This explains why alloys are
harder and stronger than the
pure metals.
Chapter 19

Quick Check 1
1. State 2 physical properties of metals which make them
useful as constructing materials.
2. What is meant by the terms: “ malleable” and
“ ductile ” ?
3. What is an “ alloy” ? Give two examples of alloys.
4. Explain why alloys are harder and stronger than the pure
metals.
5. Explain why brass is used for making the pins of the power
plug, instead of pure copper.
SolutionSolution
Chapter 19

1. (a) Metals are strong and malleable.
(b) They can withstand high temperatures.
2. Malleable means it can be hammered into sheets without
breaking; Ductile means it can be stretched into wires without
breaking.
3. An alloy is a mixture of a metal with another element. Brass and
steel are examples of alloys.
4. Unlike pure metals, the atoms in an alloy are of different sizes.
This makes it more difficult for the atoms to slide over each other
when a force is applied.
5. Brass is harder and stronger than pure copper.
Return
Solution to Quick check 1
Chapter 19

The Reactivity Series
 The Reactivity Series
shows the order of
reactivity of metals in
their reactions with
water, steam, and
dilute acids.
Potassium (K)
Sodium (Na)
Calcium (Ca)
Magnesium (Mg)
Aluminium (Al)
Zinc (Zn)
Iron (Fe)
Lead (Pb)
Copper (Cu)
Silver (Ag)
Most reactiveMost reactive
Least reactiveLeast reactive
Chapter 19

How to remember the Reactivity Series
Potassium (K)
Sodium (Na)
Calcium (Ca)
Magnesium (Mg)
Aluminium (Al)
Zinc (Zn)
Iron (Fe)
Lead (Pb)
Copper (Cu)
Silver (Ag)
Katty’s
Naughty
Cat
Mingled with
Alice and
Zarina;
Fearlessly
Plundering her
Cupboard of
Silver
Most reactive
Least reactiveLeast reactive
Chapter 19

The Reactivity Series
Potassium
Sodium
Calcium
……………......
Magnesium
Aluminium
Zinc
Iron
Lead
………………..
Copper
Silver
Most Reactive
Least Reactive
React with coldReact with cold
waterwater
ReactReact
withwith
steamsteam
Do not reactDo not react
with water,with water,
steam or dilutesteam or dilute
acidsacids
Explode withExplode with
steam andsteam and
dilute acidsdilute acids
React withReact with
dilute acidsdilute acids
withwith
decreasingdecreasing
vigourvigour
Chapter 19

Reaction of potassium with water
 The first three metals: potassium, sodium and calcium react
very vigorously with cold water to produce hydrogen gas and an
alkali.
 When a small piece of potassium is placed into a trough of
water, it immediately bursts into flames, and moves rapidly on
the water surface. The hydrogen gas given off makes it burn
explosively. An alkali, potassium hydroxide, is also formed.
2K(s) + 2H2O(l)  2KOH(aq) + H2(g)
Chapter 19

Reaction of sodium with water
 Sodium reacts less vigorously than
potassium with cold water.
 When a small piece of sodium is placed into a
trough of water, it melts into a silvery ball and
darts about on the water surface. It may
occasionally burst into flame. An alkali, sodium
hydroxide, is left in the solution.
 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)
Chapter 19

Reaction of calcium with water
 When a small piece of calcium is placed in a
beaker of water, it sinks to the bottom of the water.
It reacts vigorously with the water, producing
bubbles of hydrogen.
 The water turns slightly milky due to the
formation of calcium hydroxide, which is not
very soluble in water.
Ca(s) + 2H2O(l)  Ca(OH)2 (aq) + H2 (g)
 The hydrogen can be collected in a
test tube and tested with a lighted splint.
Chapter 19
pop

Reactions with steam
 Magnesium, zinc and iron do not react with cold
water but react with steam when heated to
produce hydrogen and a metal oxide:
 Equations:
 Mg(s) + H2O(g)  MgO(s) + H2(g)
 Zn(s) + H2O(g)  ZnO(s) + H2(g)
 3Fe(s) + 4H2O(g)  Fe3O4(s) + 4H2(g)
Chapter 19

Reaction of magnesium with steam
 When the test tube is heated,
steam is produced which reacts
with the hot magnesium ribbon.
 An experiment is set up as
shown in the diagram.
 The magnesium reacts with the steam,
producing hydrogen gas which burns at the
jet of the glass tube.
 Mg + H2O  MgO + H2
Chapter 19

Reactions with dilute acids Potassium (K)
Sodium (Na)
Calcium (Ca)
……………………
Magnesium (Mg)
Aluminium (Al)
Zinc ( Zn)
Iron (Fe)
Lead (Pb)
……………………
Copper (Cu)
Silver (Ag)
 All metals from lead and above
react with dilute acids to form a
salt and hydrogen.
 The higher the metal is in the
reactivity series, the more
vigorous the reaction.
 Potassium, sodium and
calcium will explode with
acids, while lead will only react
very slowly when heated.
React with
dilute acids
No reaction
with dilute
acids
Chapter 19

Reactions of metals with dilute hydrochloric acid
 The picture shows that magnesium reacts very vigorously with
dilute hydrochloric acid, followed by zinc.
Lead has almost no reaction with dilute hydrochloric acid.
 Copper does not react with dilute hydrochloric acid.
Chapter 19

Non-reactivity of Aluminium Potassium (K)
Sodium (Na)
Calcium (Ca)
……………………
Magnesium (Mg)
Zinc ( Zn)
Iron (Fe)
…………………
Lead (Pb)
Copper (Cu)
Silver (Ag)
 Aluminium which is
relatively high in the
Reactivity Series seems to
have no reaction with water,
steam and dilute acids.
This is because aluminium is
coated with a thin layer of aluminium
oxide that is invisible to the naked
eye. This layer protects the metal
from contact with the reagents.
Aluminium (Al)
Chapter 19

Quick Check 2
1. Which metal is (a) the most reactive, (b) the least reactive, in the
reactivity series? (Exclude silver)
2. Arrange the following metals from the most reactive to the least
reactive: calcium, zinc, magnesium, sodium, copper and aluminium.
3. What gas is given out when metals react with water and dilute acids ?
4. Write a balanced chemical equation for the following reactions:
(i) sodium and water, (ii) magnesium with steam, (iii) zinc with dilute
hydrochloric acid.
5. When a piece of aluminium was placed in a test tube containing dilute
hydrochloric acid, there was no reaction. When the aluminium was
rubbed with some sodium hydroxide solution and then re-immersed in
the hydrochloric acid, the aluminium reacted vigorously with the acid.
Explain why this happens.
Solution
Chapter 19

1. (a) Potassium, (b) copper
2. Sodium, calcium, magnesium, aluminium, zinc, copper
3. Hydrogen gas
4. (i) 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)
(ii) Mg(s) + H2O(l)  MgO(s) + H2(g)
(iii) Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g)
5. The piece of aluminium was coated with a layer of
aluminium oxide which protects it from the hydrochloric
acid. Rubbing it with sodium hydroxide removed the layer
of aluminium oxide, and hence the aluminium was able to
react with the hydrochloric acid. Return
Chapter 19

The Reactivity series and ease of forming ions
 The reactivity series is related to the ease of the metals in
forming positive ions by losing electrons.
 The more easily a metal loses its outermost electron(s), the
more reactive it will be.
 A more reactive metal will form a more stable compound with a
non-metal. Hence It is more difficult for oxides and carbonates
of the more reactive metals to be reduced or decomposed by
heat.
Chapter 19

Reduction of metal oxides
Potassium
Sodium
Calcium
Magnesium
Aluminium
Zinc
Iron
Lead
Copper
Silver
Not reduced
by hydrogen
Reduced by
hydrogen
Not reduced by
carbon
Reduced by
carbon
(Carbon)
(Hydrogen)

Reduction of metal oxides by carbon
 Oxides of metals which are below carbon in the
reactivity series are reduced to the metal when
heated with carbon.
 This process is used in the industry to obtain the
metals from their ores.
 Examples:
 ZnO(s) + C(s)  Zn(s) + CO(g)
 CuO(s) + C(s)  Cu(s) + CO(g)
Chapter 19

Reduction of metal oxides by hydrogen
 Oxides of metals which are below hydrogen in the
reactivity series are reduced to the metal when
heated with hydrogen.
Examples:
 CuO(s) + H2(g)  Cu(s) + H2O (g)
 AgO(s) + H2(g)  Ag(s) + H2O(g)
Chapter 19

Displacement Reactions
 When a piece of zinc is placed in copper(II)
sulphate solution, a brown layer of copper
is formed on the surface of the zinc.
Zinc metal
Copper
coating
Copper(II)
sulphate
solution
The zinc has displaced the copper from the
copper(II) sulphate solution because zinc is
more reactive than copper.
Zn + CuSO4  ZnSO4 + Cu
 In general, a more reactive metal will displace a less
reactive metal from their salts in solution.
Chapter 19

Displacement Reactions
 If a piece of zinc is placed in
magnesium sulphate solution,
no reaction will take place.
Zinc metal
No reaction
magnesium
sulphate
solution
 This is because zinc is less
reactive than magnesium
(lower in the reactivity
series than magnesium) and
hence cannot displace
magnesium ions from its
solution.
Chapter 19

Displacement of metal from their oxides
 A more reactive metal can
displace a less reactive metal
from its oxide when they are
heated together.
E.g. 2Al + Fe2O3  Al2O3 + 2Fe
Potassium (K)
Sodium (Na)
Calcium (Ca)
Magnesium (Mg)
Aluminium (Al)
Zinc ( Zn)
Iron (Fe)
Lead (Pb)
Copper (Cu)
Silver (Ag)
Most reactive
 This reaction is used in
the production of
“thermite”, which uses
the molten iron formed
to repair cracks on
railway lines. Least reactive
Chapter 19

Action of heat on metal carbonates
 Carbonates decompose
when heated to produce
the metal oxides and
carbon dioxide.
E.g. CaCO3  CaO + CO2
Potassium (K)
Sodium (Na)
Calcium (Ca)
Magnesium (Mg)
Aluminium (Al)
Zinc ( Zn)
Iron (Fe)
Lead (Pb)
Copper (Cu)
Silver (Ag)
Carbonates not
decomposed by
heat
Carbonates
decomposed
by heat
More difficult
Easier
 However, the more
reactive the metals
are, the more
difficult it is for their
carbonates to
decompose.
Chapter 19

Thermal stability of metallic compounds
Chapter 19

Reactions of metallic compounds
with acids and alkalis
Chapter 19

Quick Check 3
1. Arrange the following metals in order of their ease of forming positive
ions, starting from the most difficult:
lead, magnesium, sodium, iron, calcium, copper, potassium, zinc.
2. State what will happen when a piece of iron is placed in a beaker of
copper(II) sulphate solution. Write a chemical equation for the reaction.
3. Complete the following reactions.
(a) Mg(s) + ZnSO4(aq) 
(b) Zn(s) + Pb(NO3)2(aq) 
(c) Al(s)+ Zn(NO3)2(aq 
(d) Cu(s) + ZnSO4(aq) 
(e) ZnCO3(s) 
(f) Mg(s) + Al2O3(s) 
Solution
Chapter 19
heat

1. Copper, lead, iron, zinc, magnesium, calcium, sodium and potassium.
2. The iron will turn reddish-brown as it has displaced copper from the
copper(II) sulphate solution. The blue copper(II) sulphate will become
pale green in colour.
Fe(s) + CuSO4(aq)  FeSO4(aq) + Cu(s)
3. (a) Mg(s) + ZnSO4(aq) MgSO4(aq) + Zn(s)
(b) Zn(s) + Pb(NO3)2(aq)  Zn(NO3)2(aq) + Pb(s)
(c) 2Al(s)+ 3Zn(NO3)2(aq)  2Al(NO3)3(aq) + 3Zn(s)
(d) Cu(s) + ZnSO4(aq)  No reaction
(e) ZnCO3(s)  ZnO(s) + CO2(g)
(f) 3Mg(s) + Al2O3(s)  3MgO(s) + 2Al(s) Return
Chapter 19
heat

1. http://www.chemicalelements.com/groups/alkali.html
2. http://www.ndt-
ed.org/EducationResources/CommunityCollege/Materials/Introduction
/metals.htm
To Learn more about Metals, click on the
links below!
Chapter 19

C19 metals and their reactivity

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