Reactivity and the reactions of metals


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+


Investigating reactivity with oxygen


Order of reactivity with oxygen


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+


What happens to the mass?


Metals and oxygen: true or false?


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?


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!


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:


Investigating reactivity with water (I)


Equations: reactions of metals with water


2Na 2H2O 2NaOH H2+ +

sodium watersodium

hydroxidehydrogen+ +

2Li 2H2O 2LiOH H2+ +

+ waterlithium

hydroxide hydrogenlithium +

2K 2H2O 2KOH H2+ +

potassium waterpotassiumhydroxide

hydrogen+ +


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?


Order of reactivity with water


Odd one out


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 +


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?


What is needed for iron to rust?


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


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


Rusting: true or false?


Reacting metals with acid


Order of reactivity with acid


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.

incr

easi

ng

rea

ctiv

ity

Reactivity of metals

calcium

sodium

copper

hydrogen

lead

iron

zinc

aluminium

magnesium


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+ +


Metals and hydrochloric acid – equations


hydrochloricacid

magnesiumchloride

magnesium hydrogen+ +

Mg 2HCl MgCl2 H2+ +

aluminium hydrochloricacid

aluminium

chloride

hydrogen+ +

2Al 6HCl 2AlCl3 3H2+ +

zinc hydrochloricacid

zincchloride

hydrogen+ +

Zn 2HCl ZnCl2 H2+ +


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.


What is the equation?


Word equations for metals and acids


Balancing equations for metals and acids


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?


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:

pleasesend

charlie’smonkeys

andzebras

inlargecages

securelyguarded!


What is the order of reactivity?


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.

potassiumsodiumcalcium

magnesiumaluminium

zincironlead

coppersilvergold

incr

easi

ng

rea

ctiv

ity


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


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.


The reactivity series: summary


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.

aluminiumiron

oxideiron+

aluminium oxide +

In this reaction, aluminium reacts with iron oxide to make aluminium oxide and iron.


Displacement in action

What happens when magnesium reacts with copper sulfate?

magnesiumcopper 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


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

lessreactive metal

compound

morereactive metal

compound

less reactive

metal+ +

less reactive metal

more reactive metal compound

no reaction+


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.

magnesiumcopper

chloridecopper+

magnesium chloride +

magnesium chloride+ no reactionsilver


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+ +


Displacement reactions – activity


Displacement reactions

Use the reactivity series to predict if each mixture will react and complete the word equation.

magnesiumaluminium

oxide+ magnesium

oxidealuminium+

ironchloride

magnesium + magnesium

chlorideiron+

copper gold nitrate+ coppernitrate

gold+

silver zinc oxide no reaction+


Glossary


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Reactivity and the reactions of metals

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