A list of elements (usually metals) arranged in an order to show how easily they form compounds.
Some elements arranged in order of chemical activity. The rate of chemical reactivity increases as you go up the list
| Metals nearer the top of the list will
Showing that metals have different reactivities
Reacting metals with dilute hydrochloric acid
1 spatula each of powdered magnesium, powdered zinc, iron filings and copper turnings are each placed separately in a test tube containing equal volumes of dilute hydrochloric acid. All observations are noted
|Magnesium||Reacted vigorously producing large amounts of gas.
The mixture became quite hot
|Zinc||Bubbled steadily. The mixture became warm|
|Iron||Bubbled very slowly.|
|Copper||Mo visible reaction|
Metals react with an acid to produce hydrogen gas.
The reactive metals like magnesium reacted much more vigorously than the less reactive metals like zinc and iron.
The test for hydrogen is that it burns with a squeaky ‘pop’.
Oxidation and reduction
Any element in the list will always be able to reduce (take oxygen away from) the oxide of an element lower down in the list.
Heating magnesium powder with copper oxide
Some copper oxide is mixed with powdered magnesium on a crucible lid and heated strongly
A violent exothermic reaction. The copper oxide was reduced by the magnesium to leave magnesium oxide and copper.
(The heat of the reaction makes most of the copper turn back to copper oxide)
Word Equation: Magnesium + copper oxide —-> magnesium oxide + copper
The copper oxide has been reduced by the magnesium.
The magnesium has been oxidised by the copper oxide.
The reaction above shows us that magnesium is MORE reactive than copper.
When magnesium reacts with copper oxide the magnesium is oxidised and the copper oxide is reduced.
Heating zinc powder with magnesium oxide
NOTHING will happen.
The zinc cannot reduce the magnesium oxide. This shows us that zinc is LESS reactive then magnesium.
Carbon is of special interest. It is not a metal but can still be used to reduce the oxide of a metal
example: Heating copper oxide with carbon
Experiment: Mix powdered wood charcoal (carbon) with copper oxide and heat the mixture strongly.
Observation: a red glow spreads though the mixture which shows that a chemical reaction is taking place. A residue of pik copper is seen after the mixture has cooled.
Explanation: The carbon in the charcoal is more reactive than copper so reduces the copper oxide, leaving pink copper metal. Crabon dioxide is also made during the reaction
Word equation: Carbon + copper oxide → copper + carbon dioxide↑
This reaction is useful because it gives us a method for extracting copper from its ores found in the ground.
Carbon is particularly useful for obtaining iron from iron ore (which contains iron oxide)
Word equation: Carbon + iron oxide → iron+ carbon dioxide↑
This is not an easy reaction to do in the laboratory but it shows the reaction that goes on in factories that make iron from iron ore
Another example: If Some magnesium ribbon is plunged into a gas jar containing carbon dioxide gas the magnesium will reduce the carbon dioxide to leave black specks of carbon and magnesium oxide
Word equation: Magnesium + carbon dioxide —> magnesium dioxide + carbon
Experiment: Some iron filings are placed in a blue solution of copper sulphate
The copper sulphate loses its colour and the iron goes pink because it gets a coating of pink copper.
the solution also gets warm which shows that a chemical reaction is taking place.
Explanation: The iron is more reactive than copper and displaces (pushes out) the copper from the solution.
Word equation: Copper sulphate + Iron —-> iron sulphate + copper
When iron is added to copper sulphate solution the copper is displaced by the iron.
Calcium metal will reduce water to form hydrogen gas and leave a white residue of calcium oxide.
This reaction shows us that calcium is more reactive than hydrogen.
(* remember that water is an oxide of hydrogen)
Word equation: Calcium + water —> calcium oxide + hydrogen
Reduce: To take oxygen away from a compound.
Oxidise: When a chemical gets oxygen added to it
Displace: When a metal is pushed out of a solution by another, more reactive metal
Exothermic: A reaction which gives out heat