Transcript 9F Patterns of Reactivity

IGCSE Chemistry
10.5.1 Patterns of
Reactivity
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Contents
9F Patterns of Reactivity
Metals and water
Metals and oxygen
Metals and acid
Reactivity series and displacement
Summary activities
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Metals and water
The Romans used lead to make water pipes but didn’t know
that lead reacts slowly with water and makes it poisonous!
Some metals react vigorously with water, some metals react
slowly and some do not react at all.
What is the best type of metal to use for water pipes?
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Metals and water – general equation
Potassium and sodium are metals that react vigorously with
water even when a small amount of each metal is used.
When a metal reacts with water, the products are a metal
hydroxide and hydrogen gas. What is the general equation
for the reaction of a metal with water?
metal
water
metal
hydroxide
hydrogen
What is the test that a metal hydroxide is produced?
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Metals and water – equations
What are the products when each metal reacts with water?
What is the balanced symbol equation for each reaction?
lithium
+
water

lithium
hydroxide
+
hydrogen
2Li
+
2H2O

2LiOH
+
H2
sodium
+
water

sodium
hydroxide
+
hydrogen
2Na
+
2H2O

2NaOH
+
H2
potassium +
water
 potassium
hydroxide
+
hydrogen
2H2O

+
H2
2K
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+
2KOH
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Metals and water – observations
James investigated how reactive some metals are when
they react with water and made these observations.
Metal
Reaction with water
lithium
Bubbles of gas are given off quite
quickly. When tested with universal
indicator the water is now alkaline.
sodium
The sodium melts and skims over the
surface producing a stream of small
bubbles. Sometimes a yellow-orange
flame appeared.
potassium
Potassium immediately produces a lilac
flame as it skims around the surface
making a fizzing noise.
Which of these metals is the most reactive with water?
Which of these metals is the least reactive with water?
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Metals and water – more observations
James investigated how reactive other metals are with water
and made these observations.
Metal
Reaction with water
magnesium
Reacts slowly with cold water
but reacts quickly with steam.
copper
No reaction.
silver
No reaction.
gold
No reaction.
Copper is used in plumbing and silver and gold in jewellery.
Why are these unreactive metals suitable for such uses?
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Metals and water – using unreactive metals
The words “plumber” and
“plumbing” come from
plumbum (the Latin word
for lead) because the
ancient Romans used lead
for their water pipes.
Lead reacts very slowly with water
making it poisonous, so this metal
is no longer used in plumbing.
Copper is a much better metal for
water pipes because it does not
react at all with water – plumbers
should be renamed coppers!
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Metals and water – order of reactivity
Put the following metals in order of reactivity based on their
reaction with water, starting with the most reactive:
copper, gold, magnesium, lithium, potassium, silver, sodium.
potassium
sodium
lithium
magnesium
copper, silver, gold
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Contents
10.5.1 Patterns of Reactivity
Metals and water
Metals and oxygen
Metals and acid
Reactivity series and displacement
Summary activities
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Metals and oxygen – general equation
Most metals will react with oxygen. Some metals react faster
than others and some may react very slowly or not at all.
Magnesium, for example, burns in
oxygen with a bright flame.
The magnesium reacts with oxygen
to produce magnesium oxide.
When a metal does react with oxygen, the product is a
metal oxide. What is the general equation for the reaction
of a metal with oxygen?
metal
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oxygen
metal
oxide
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Metals and oxygen – equations
What are the products when each metal reacts with oxygen?
What is the balanced symbol equation for each reaction?
magnesium +
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oxygen
 magnesium oxide
2Mg
+
O2

2MgO
copper
+
oxygen

copper oxide
2Cu
+
O2

2CuO
iron
+
oxygen

iron oxide
4Fe
+
3O2

2Fe2O3
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Metals and oxygen – observations
Shaida investigated how reactive some metals are when
they react with oxygen and made these observations.
Metal
Reaction with oxygen
magnesium
The ribbon burned with a dazzling
white flame giving grey-white smoke
and ash.
copper
The copper turnings went through
reds and oranges and then slowly got
a permanent coating of black.
iron
The iron filings glowed red and
sparkled leaving a brown-black
looking solid.
Which of these metals is the most reactive with oxygen?
Which of these metals is the least reactive with oxygen?
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Metals and oxygen – order of reactivity
Put the following metals in order of reactivity based on their
reaction with oxygen, starting with the most reactive:
copper, iron, magnesium.
magnesium
iron
copper
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Contents
10.5.1 Patterns of Reactivity
Metals and water
Metals and oxygen
Metals and acid
Reactivity series and displacement
Summary activities
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Metals and acid – the acid test
The first scientists to study chemistry
were called alchemists. They were
interested in many things including
finding ways of changing cheap
metals into gold. Some were very
good at making metals look gold.
Acid was used to find out if gold objects were made of real or
fake gold. Most metals react with strong acids. Gold is such
an unreactive metal that it does not react with strong acids.
This became known as “the acid test” because it stopped
tricksters making false claims that something was gold.
The phrase “the acid test” is used today to mean any
process that will reveal fakes.
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Metals and acid – experiment
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Metals and acid – general equation
Gold is an unreactive metal that does not react with acid.
Other metals, such as magnesium
and zinc, react with acid producing
bubbles of gas.
The “squeaky pop” test shows that
this gas is hydrogen.
When a metal reacts with acid, the products are a metal salt
and hydrogen. What is the general equation for the reaction
of a metal with acid?
metal
acid
metal salt
hydrogen
How does the type of acid affect the type of salt produced?
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Metals and hydrochloric acid – equations
What is made when each metal reacts with hydrochloric acid?
What is the balanced symbol equation for each reaction?
magnesium
Mg
aluminium
2Al
zinc
Zn
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+ hydrochloric  magnesium +
acid
chloride
hydrogen

H2
+
2HCl
MgCl2
+
+ hydrochloric  aluminium +
acid
chloride
hydrogen

3H2
+
6HCl
+ hydrochloric 
acid
+
2HCl

2AlCl3
zinc
chloride
ZnCl2
+
+
+
hydrogen
H2
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Metals and sulfuric acid – equations
What is made when each metal reacts with sulfuric acid?
What is the balanced symbol equation for each reaction?
magnesium +
Mg
+
aluminium +
2Al
zinc
Zn
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+
+
+
sulfuric
acid
 magnesium +
sulfate
H2SO4

sulfuric
acid
 aluminium
sulfate
3H2SO4

Al2(SO4)3 +
sulfuric
acid

zinc
sulfate
H2SO4

ZnSO4
MgSO4
+
+
+
+
hydrogen
H2
hydrogen
3H2
hydrogen
H2
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Metals and nitric acid – equations
What is made when each metal reacts with nitric acid?
What is the balanced symbol equation for each reaction?
magnesium +
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nitric acid
Mg
+
2HNO3
aluminium
+
nitric acid
2Al
+
6HNO3
zinc
+
nitric acid
Zn
+
2HNO3
 magnesium +
nitrate

Mg(NO3)2
 aluminium
nitrate

+
+
2Al(NO3)3 +
 zinc nitrate +

Zn(NO3)2
+
hydrogen
H2
hydrogen
3H2
hydrogen
H2
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Metals and acid – observations
Greg investigated how reactive some metals are with hot
and cold acid and made these observations.
Metal
magnesium
aluminium
copper
iron
lead
calcium
zinc
Reaction with
cold acid (HCl)
Reaction with
hot acid (HCl)
Fizzed rapidly
-
-
Bubbled quickly
No reaction
No reaction
No reaction
Slow bubbling
No reaction
Occasional bubble
Really fast
-
Moderate bubbling
-
Which of these metals is the most reactive with acid?
Which of these metals is the least reactive with acid?
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Metals and acid – order of reactivity
Put the following metals in order of reactivity based on their
reaction with acid, starting with the most reactive:
aluminium, calcium, copper, iron, lead, magnesium, zinc.
calcium
magnesium
aluminium
zinc
iron
lead
copper
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Metals and acid – reactivity activity
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Contents
10.5.1 Patterns of Reactivity
Metals and water
Metals and oxygen
Metals and acid
Reactivity series and displacement
Summary activities
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Comparing orders of reactivity
When the orders of reactivity of metals with water, oxygen
and air are compared, there is a pattern of results.
with water
with oxygen
with acid
potassium
sodium
lithium
magnesium
copper
silver
gold
magnesium
iron
copper
calcium
magnesium
aluminium
zinc
iron
lead
copper
Combining the information from all the reactions of metals
with water, oxygen and air gives an overall order of reactivity
called the reactivity series.
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The reactivity series
increasing reactivity
The reactivity series is the list of metals placed in order of
their reactivity.
One way to remember this order is to learn this silly sentence:
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potassium
sodium
calcium
magnesium
aluminium
zinc
iron
lead
copper
silver
gold
Please
send
Charlie’s
monkeys
and
zebras
in
lead
cages
securely
guarded!
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What is the order of metals?
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Using the reactivity series
 Predictions can be made
about simple reactions of
metals with oxygen, water
and acids.
 Predictions can also be
made about more complex
reactions where one metal
is competing with another.
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increasing reactivity
The reactivity series can be used to make predictions
about the reactions of metals.
potassium
sodium
calcium
magnesium
aluminium
zinc
iron
lead
copper
silver
gold
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Simple reactions – predictions
Use the reactivity series to predict if a reaction will take place
and how intense the reaction will be.
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Metal
React
with
gold
acid
Prediction
no reaction
calcium water
fizzing
sodium oxygen
burns vigorously
silver
oxygen
very slow reaction
zinc
oxygen
burns moderately
potassium
sodium
calcium
magnesium
aluminium
zinc
iron
lead
copper
silver
gold
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When does displacement happen?
The reactivity series can be used to predict if a metal will
react with a metal compound (e.g. chloride, nitrate or sulfate).
 If the metal is more reactive than the metal in the compound,
it competes with the less reactive metal.
more reactive less reactive
more reactive less reactive

+
+
metal
metal
metal
metal
compound
compound
The more reactive metal pushes out, or displaces, the less
reactive metal from its compound.
 If the metal is less reactive than the metal in the compound,
it will not compete and so there is no reaction.
less reactive
metal
reactive

+ moremetal
no reaction
compound
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Displacement reactions – examples
The reactivity series can be used to predict if a metal will
react with a metal compound.
 Will magnesium react with copper chloride?
magnesium +
copper
chloride
 magnesium +
chloride
copper
Magnesium is a more reactive metal than copper, so
magnesium displaces the copper from its compound.
 Will silver react with magnesium chloride?
silver
+ magnesium  no reaction
chloride
Silver is a less reactive metal than magnesium, so silver
does not displace the magnesium from its compound.
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Displacement reactions – observation
This photograph shows what
happens when magnesium
reacts with copper sulfate.
before
after
Why does the blue colour of
the coppers sulfate solution
gradually disappear during
this reaction?
magnesium +
copper
sulfate
 magnesium +
sulfate
copper
Magnesium is a more reactive metal than copper and so
the magnesium displaces the copper from the copper
sulfate solution. This is why the blue colour disappears.
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Displacement of sulfates – predictions
Use the reactivity series to predict if there is a reaction when
these metals are added to different metal sulfate solutions.
metal sulfate magnesium
solution
sulfate
metal
magnesium
zinc
iron
copper




zinc
sulfate
iron
sulfate
copper
sulfate









= displacement reaction
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
= no reaction
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Displacement of sulfates – magnesium
Does magnesium react with and displace these metal sulfates
and if so what products are formed?

copper
sulfate
 magnesium +
sulfate
CuSO4

zinc
sulfate
 magnesium +
sulfate
zinc
+
ZnSO4

Zn
magnesium +
iron
sulfate
 magnesium +
sulfate
iron
FeSO4

Fe
magnesium +
Mg

magnesium +
Mg

Mg
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+
+
MgSO4
MgSO4
MgSO4
+
+
+
copper
Cu
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Displacement of sulfates – zinc
Does zinc react with and displace these metal sulfates
and if so what products are formed?



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zinc
+ magnesium  no reaction
sulfate
zinc
+
iron
sulfate

zinc
sulfate
+
iron
Zn
+
FeSO4

ZnSO4
+
Fe
zinc
+
copper
sulfate

zinc
sulfate
+
copper
Zn
+
CuSO4

ZnSO4
+
Cu
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Displacement of sulfates – iron
Does iron react with and displace these metal sulfates
and if so what products are formed?



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iron
+ magnesium  no reaction
sulfate
iron
+
zinc
sulfate
 no reaction
iron
+
copper
sulfate

iron
sulfate
+
copper
Fe
+
CuSO4

FeSO4
+
Cu
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Displacement of sulfates – copper
Does copper react with and displace these metal sulfates
and if so what products are formed?

copper
+ magnesium  no reaction
sulfate

copper
+
zinc
sulfate
 no reaction

copper
+
copper
sulfate
 no reaction
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Displacement of oxides
Displacement reactions can also occur between a metal
and a metal compound that is a solid.
aluminium +
iron
oxide
 aluminium
oxide
+
iron
The more reactive aluminium wins the oxygen from the less
reactive iron. The reaction gets so hot that the iron melts!
This is the Thermit reaction and is used to weld railway lines.
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Displacement of oxides – predictions
Use the reactivity series to predict if there is a reaction when
each mixture of a metal and a metal oxide is heated.
metal
oxide
metal
zinc
oxide
zinc
iron
copper



= displacement reaction
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iron
oxide
copper
oxide





= no reaction
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Displacement of oxides – zinc
Does zinc react with and displace these metal oxides
and if so what products are formed?


 zinc oxide
zinc
+
copper
oxide
Zn
+
CuO

 zinc oxide
+
iron

+
2Fe
zinc
+
iron
oxide
3Zn
+
2Fe2O3
+
ZnO
3ZnO
copper
Cu
 Zinc is the more reactive than copper and iron.
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Displacement of oxides – iron
Does iron react with and displace these metal oxides
and if so what products are formed?


 no reaction
iron
+
zinc
oxide
iron
+
copper
oxide

iron oxide
+
copper
2Fe
+
3CuO

Fe2O3
+
3Cu
 Iron is less reactive than zinc but more reactive than copper.
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Displacement of oxides – copper
Does copper react with and displace these metal oxides
and if so what products are formed?


copper
+
zinc
oxide
 no reaction
copper
+
iron
oxide
 no reaction
 Copper is less reactive than zinc and iron and will not
displace either of these metals.
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Displacement reactions – activity
Use the reactivity series to predict if each mixture will react.
Reactants
iron oxide
magnesium
copper
sulfate
potassium
zinc
gold
calcium
calcium
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hydrochloric
acid
iron
chloride
sodium
chloride
oxygen
Reaction?






potassium
sodium
calcium
magnesium
aluminium
zinc
iron
lead
copper
silver
gold
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Displacement reactions – activity
Use the reactivity series to predict if each mixture will react
and complete the word equation.
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aluminium  magnesium + aluminium
oxide
oxide
magnesiu
m
+
magnesiu
m
+
iron
chloride
silver
+
zinc
oxide
 no reaction
copper
+
gold
nitrate

 magnesium +
chloride
copper
nitrate
+
iron
gold
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Contents
10.5.1 Patterns of Reactivity
Metals and water
Metals and oxygen
Metals and acid
Reactivity series and displacement
Summary activities
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Glossary
displaced metal – The metal that is pushed out of a
compound by a more reactive metal.
displacement – A reaction in which a more reactive
metal replaces a less reactive metal in a compound.
reactive – A substance that reacts quickly or easily.
reactivity – How quickly or easily a substance will react.
reactivity series – The list of metals placed in order of
their reactivity starting with the most reactive.
tarnished – A metal that has become dull after reacting
with water and oxygen in the air.
Thermit reaction – The displacement reaction between
aluminium and iron oxide that is used to weld railway lines.
unreactive – A substance that reacts very slowly or
does not react at all.
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Anagrams
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True or false?
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Multiple-choice quiz
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