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Reactivity and the_reactions_of_metals
- 3. © Boardworks Ltd 20083 of 53
Reacting metals with oxygen
Most metals react with oxygen.
Some metals react quickly
and some only react very
slowly. Magnesium, for
example, burns in oxygen
with a bright flame.
When a metal reacts with oxygen, the product is a metal oxide.
This is called an oxidation reaction.
metal oxygen metal oxide+
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Equations: reactions of metals with oxygen
What is the balanced symbol equation for each reaction?
4Fe O2 2Fe2O3+
iron oxygen iron oxide+
2Cu O2 2CuO+
+ oxygen copper oxidecopper
2Mg O2 2MgO+
magnesium oxygen magnesium oxide+
- 10. © Boardworks Ltd 200810 of 53
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.
Which is the best type of metal to use for water pipes?
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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.
Why is lead no longer
used in plumbing?
Copper is a much better
metal for water pipes because
it does not react at all with
water – perhaps plumbers
should be renamed coppers!
- 12. © Boardworks Ltd 200812 of 53
Reacting metals with water
When any metal reacts
with water, the products
are a metal hydroxide
and hydrogen gas.
What tests could you do to show that hydrogen and a
hydroxide have been produced?
metal water metal hydroxide hydrogen+ +
This is the general
equation for the reaction
of a metal with water:
- 14. © Boardworks Ltd 200814 of 53
Equations: reactions of metals with water
What is the balanced symbol equation for each reaction?
2Na 2H2O 2NaOH H2+ +
sodium water
sodium
hydroxide
hydrogen+ +
2Li 2H2O 2LiOH H2+ +
+ water
lithium
hydroxide hydrogenlithium +
2K 2H2O 2KOH H2+ +
potassium water
potassium
hydroxide
hydrogen+ +
- 15. © Boardworks Ltd 200815 of 53
Investigating reactivity with water (II)
James investigated how reactive some metals were with water.
He made these observations:
reacts slowly with cold water but reacts
quickly with steamgold
metal reaction with water
calcium
no reaction
no reactionsilver
zinc
no reaction
Copper is used in plumbing and silver and gold in jewellery.
Why are these unreactive metals suitable for such uses?
- 19. © Boardworks Ltd 200819 of 53
Corrosion of metals
Metals corrode when they are
left in contact with air or water.
Which metals corrode quickly
and which corrode slowly?
When iron corrodes, it is called rusting.
Rusting is the oxidation reaction of iron
with oxygen in the presence of water.
oxygen iron oxideiron +
3O2 Fe2O32Fe +
- 20. © Boardworks Ltd 200820 of 53
Does salt make iron rust faster?
People who live by the seaside often claim that their cars go
rusty faster.
Does salt speed up the rate of the rusting reaction?
- 22. © Boardworks Ltd 200822 of 53
Preventing rust
Rusting destroys a huge amount of iron and steel every day.
People spend a lot of money making sure that their iron and
steel buildings, engines, lorries and ships do not rust.
What methods could you use to prevent things rusting?
painting plastic coating
oilinggalvanising
- 23. © Boardworks Ltd 200823 of 53
Rusting: sacrificial protection
Sacrificial protection is another way of preventing rust.
This involves attaching big blocks
of magnesium or zinc to the iron
hull of a ship or water pipe.
Because magnesium is
more reactive than iron,
it corrodes first, leaving
the iron intact.
Eventually the magnesium
blocks have to be replaced
because they have
corroded completely away.
iron
reactive
metal
- 28. © Boardworks Ltd 200828 of 53
This list is called the
reactivity series.
The more reactive
the metal, the more
vigorous the reaction.
Metals can be listed in order
of how reactive they are.
A metal that is below
hydrogen will not react
with dilute acids.
increasingreactivity
Reactivity of metals
calcium
sodium
copper
hydrogen
lead
iron
zinc
aluminium
magnesium
- 29. © Boardworks Ltd 200829 of 53
Products of metal reacting with acid
When metals react with acid, bubbles of gas are produced.
The ‘squeaky pop’ test shows
that this gas is hydrogen.
When a metal reacts with acid,
the products are hydrogen gas
and a metal salt. What is the
general equation for the
reaction of a metal with acid?
metal acid metal salt hydrogen+ +
- 30. © Boardworks Ltd 200830 of 53
Metals and hydrochloric acid – equations
What is the balanced symbol equation for each reaction?
hydrochloric
acid
magnesium
chloride
magnesium hydrogen+ +
Mg 2HCl MgCl2 H2+ +
aluminium hydrochloric
acid
aluminium
chloride
hydrogen+ +
2Al 6HCl 2AlCl3 3H2+ +
zinc hydrochloric
acid
zinc
chloride
hydrogen+ +
Zn 2HCl ZnCl2 H2+ +
- 31. © Boardworks Ltd 200831 of 53
Reaction of metals with acids
When a metal reacts with an acid, the products are a salt and
hydrogen gas.
metal acid salt hydrogen+ +
The salt produced depends on the metal and type of acid
involved in the reaction:
When a metal reacts with hydrochloric acid, the salt
produced is a metal chloride.
When a metal reacts with sulfuric acid, the salt produced
is a metal sulfate.
When a metal reacts with nitric acid, the salt produced is
a metal nitrate.
- 36. © Boardworks Ltd 200836 of 53
Comparing reactivity
The orders of reactivity of metals with water, oxygen and air
can be compared.
with water
lithium
copper
gold
sodium
magnesium
silver
potassium
with oxygen
zinc
lead
magnesium
iron
copper
calcium
with acid
aluminium
iron
copper
magnesium
zinc
lead
calcium
What patterns can you see in these lists?
- 37. © Boardworks Ltd 200837 of 53
The reactivity series
Combining the information from all the reactions gives an
overall order of reactivity called the reactivity series.
One way to remember this order is to learn this silly sentence:
please
send
charlie’s
monkeys
and
zebras
in
large
cages
securely
guarded!
- 39. © Boardworks Ltd 200839 of 53
Using the reactivity series
The reactivity series can be used to make predictions about
the reactions of metals.
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.
potassium
sodium
calcium
magnesium
aluminium
zinc
iron
lead
copper
silver
gold
increasingreactivity
- 40. © Boardworks Ltd 200840 of 53
Predicting simple reactions
Use the reactivity series to predict if a reaction will take place
and how intense the reaction will be:
acidgold
metal reacts with
calcium
sodium oxygen
oxygen
oxygensilver
prediction
zinc
water
no reaction
fizzing
burns vigorously
very slow reaction
burns moderately
- 41. © Boardworks Ltd 200841 of 53
oxygen in the
atmosphere
coating of
oxygen atoms
aluminium
atoms
Aluminium
According to the reactivity series, aluminium should be a fairly
reactive metal, but in reality it often appears unreactive. Why?
This is because a protective layer of aluminium oxide quickly
forms on its surface, which stops it reacting. This means
aluminium can be used to build aeroplanes and saucepans.
However, if the
protective layer
is removed, the
aluminium
reacts more
quickly.
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What is a displacement reaction?
The Thermit reaction is an example
of a displacement reaction.
The more reactive aluminium takes the oxygen from the
less reactive iron.
The reaction gets so hot that the iron melts! It is used to weld
railway tracks.
aluminium
iron
oxide
iron+
aluminium
oxide
+
In this reaction, aluminium reacts
with iron oxide to make aluminium
oxide and iron.
- 44. © Boardworks Ltd 200844 of 53
Displacement in action
What happens when magnesium
reacts with copper sulfate?
magnesium
copper
sulfate
copper+
magnesium
sulfate
+
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.
Why does the blue colour of the
copper sulfate solution gradually
disappear during this reaction?
before after
- 45. © Boardworks Ltd 200845 of 53
Explaining displacement reactions
The reactivity series can be used to predict if a metal will react
with a metal compound. If the metal is more reactive than the
metal in the compound, it 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.
more
reactive
metal
less
reactive metal
compound
more
reactive metal
compound
less
reactive
metal
+ +
less reactive
metal
more reactive metal
compound
no
reaction
+
- 46. © Boardworks Ltd 200846 of 53
Displacement reactions – examples
Will magnesium react with copper chloride?
Magnesium is a more reactive metal than copper, so
magnesium displaces the copper from its compound.
Will silver react with magnesium chloride?
Silver is a less reactive metal than magnesium, so silver does
not displace the magnesium from its compound.
magnesium
copper
chloride
copper+
magnesium
chloride
+
magnesium
chloride
+ no reactionsilver
- 47. © Boardworks Ltd 200847 of 53
Displacement in extracting metals
Displacement reactions can
be used to extract metals
from their ores.
For example, iron and
copper are extracted from
their oxides by reacting the
ores with carbon:
iron oxide carbon carbon dioxide iron+ +
copper oxide carbon carbon dioxide copper+ +
- 49. © Boardworks Ltd 200849 of 53
Displacement reactions
Use the reactivity series to predict if each mixture will react and
complete the word equation.
magnesium
aluminium
oxide
+
magnesium
oxide
aluminium+
iron
chloride
magnesium +
magnesium
chloride
iron+
copper gold nitrate+
copper
nitrate
gold+
silver zinc oxide no reaction+
