Look at how magnesium reacts with oxygen:
The use of a gas jar full of oxygen can be used to combust other metals. This method can be used to compare different metals and their reactivity with oxygen by observing the reaction.
Metals that react with oxygen produce oxides as their products.
Of course, other metals react with oxygen, some more than sodium, for example, potassium. Others, such as gold, do not react at all.
Some metals also react with water, but like their reaction with oxygen, they react in different ways. We can observe the reaction of metals and water by placing the metals in a trough of cold water.
Alternatively, we can observe the difference in reaction of metals using steam (hot water) instead of cold water.
The table below illustrates the observations taken when different metals are placed in water:
Note: The first three in the table above produce hydroxides and the rest, if they react, produce oxides.
The production of the hydroxide (alkali) can be tested by adding universal indicator (UI) to the reaction vessel - UI changes from green to purple in the presence of these hydroxides.
To test for the release of hydrogen gas, place a lighted splint over the reacting metal - if it 'pops' then hydrogen is present.
In the case of potassium, this reaction produces enough heat to set alight the hydrogen gas itself.
Let's now look at the reaction between metals and acids to see if they can also help distinguish difference in reactivity.
If we compare the results of the reaction of metals with acid with those of the reactions with oxygen and water, we note that the same order of reactivity is repeated.
Look at the reaction below:
Here, we witness iron and copper competing to be compounds in solution. Iron wins as it displaces copper from copper sulphate solution. Green iron II sulphate is formed.
Other metals displace less reactive metals in a similar manner.
A compound will always displace a less reactive metal from solutions of its compounds.
Another example of 'competition' between metals to form compounds is observed in the reaction between metals and metal oxides.
Observe the reaction between iron and copper oxide, mixed and heated strongly.
Iron displaces the copper from the oxide - in fact iron is behaving as a reducing agent, since it is removing oxygen from the other metal.
Other metals compete in a similar way. The general rule is:
By comparing the reactions of metals in oxygen, water and acid, metal oxides and solutions of metal salts, we can arrange metals into a list of reactivity called the Reactivity Series.
The more reactive a metal is the more likely it is to form a compound.
The more reactive a metal, the more stable its compound.
The more reactive a metal the more difficult it is to extract from its compounds.
Copper, silver and gold appear as elements in the earth due to their unreactivity with their environment. They are easy to extract.
Reactive metals are more difficult to extract. They are often found as compounds or ores.
A method of extraction known as Electrolysis is used to remove the element from the remaining compound.
a) What would you expect to see if zinc metal was placed in to copper sulphate solution?
b) What are the products formed in this reaction?
(Marks available: 4)
Answer outline and marking scheme for question: 1
a) Grey metal turns brown/brown metal displaced.
Blue solution turns colourless.
(Total = 4 marks)
Complete the following equations to show what happens when metals are heated with oxides of other metals.
a) magnesium + copper oxide =
b) lead + tin oxide =
c) Fe2O3(s) + 3Zn(s) =
Answer outline and marking scheme for question: 2
a) magnesium oxide + copper
b) No reaction.
c) 3ZnO(s) + 2Fe(s)
(1 mark for formula, 1 mark for balanced equation)
When iron oxide is heated with aluminium powder, the following reaction takes place:
Aluminium + iron oxide → iron + aluminium oxide
When aluminium oxide is heated with iron no reaction takes place.
a) Which of the two metals is more reactive?
b) The formula for iron oxide is Fe2O3. The formula for aluminium oxide is Al2O3.
Write a balanced symbol equation to show the reaction between aluminium and iron oxide.
c) Window frames made from aluminium do not corrode as quickly as windows made form iron.
Explain this statement using the information above.
Answer outline and marking scheme for question: 3
b) 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s)
c) Aluminium should corrode faster than iron because it is more reactive,
It does not because the aluminium reacts with oxygen in the air to form a layer of oxide, which protects the aluminium.
(When iron oxide forms, it flakes off exposing fresh iron underneath).
Common Metals and Non-Metals
The uses of metals are related to their properties:
They are made into jewellery due to their hard and shiny appearance.
They are used to make pans, since they are good conductors of heat.
They are used in electrical cables, because they are malleable, ductile and good conductors of electricity.
They are strong so used to build scaffolding and bridges.
They make a ringing sound, sonorous, hence their use in bell making.
Used as insulating material around wire cables since they do not conduct electricity.
Used to make pan handles as they are poor conductors of heat.
Metals have high melting and boiling points.
Metals are good conductors of heat and electricity.
Non-metals are poor conductors of heat and electricity.
Non-metals have low melting and boiling points.
Some metals react oxygen to form oxides.
Some metals react with water to form salts. Potassium, sodium and calcium
form hydroxides, for example, alkaline solutions. Magnesium and other less
reactive metals form oxides.
Although many metals react with oxygen, water or even dilute acids, they
react differently. Some metals are more reactive than others.
The Reactivity Series is a
list of metals in order of reactivity.
A metal will always displace a less reactive metal from solutions of its
compound - displacement reactions.
This is because the more reactive the metal, the more easily it gives up electrons.