Programme Outline
This programme uses laboratory demonstrations and graphics to illustrate and explain patterns of reactivity of various metals. Some of the demonstrations could be duplicated in a school laboratory and used in conjunction with the programme, which employs graphics to highlight what is being illustrated.
The programme is divided into three sequences:
- 1.Group I
- 2.Group VII
- 3.Metals
The programme could be used at any stage of the teaching of patterns of reactivity of the metals chosen and would make an excellent summary or revision aid. It could be shown in full or in discrete sections as appropriate.
Group I
00.00 The appearance and reactivity of the Group I metals
Group I metals are soft and corrode quickly when exposed to air.
01.19 Comparing the reactivities of Group I metals
The reactions of these metals with water always produce the metal hydroxide, which is an alkali, and hydrogen gas. But Group I metals are more reactive the further down the group they are.
Group VII
04.00 Appearance and occurrence of the halogens
The halogens are a group of reactive, coloured elements whose melting points increase down the group. Chlorine and bromine are found in compounds dissolved in sea water. Iodine is found in seaweed.
05.12 Reactions with iron wool
Iodine vapour reacts slowly with iron wool to give brown iron iodide. The reaction of iron wool with bromine is faster and produces brown iron bromide. Iron undergoes a very rapid exothermic reaction with chlorine, giving iron chloride, a yellow sublimate.
07.27 Reactions with aluminium
The halogens - chlorine, bromine and iodine - react in different ways with aluminium. These reactions provide further evidence of the reactivity trend which is found in Group VII.
Metals
08.38 The reactivity of metals
Gold is an unreactive metal, but the alkali metals can be dangerously reactive. Metals often differ widely in their reactivity.
09.09 Displacement reactions of metals
Silver and copper will not displace lead from a solution of lead nitrate, but magnesium and zinc will. Magnesium will also displace zinc from a solution of a zinc salt, showing that magnesium is the most reactive of this group of metals.
The least reactive metal is silver, which is displaced from a silver solution by copper metal.
10.55 Zinc and copper oxide
Zinc reacts exothermically with copper oxide. Zinc oxide is one of the reaction products. Adding the reaction mixture to dilute acid separates copper, the other product.
12.02 Aluminium and iron oxide
Aluminium reacts violently with iron oxide, giving aluminium oxide and iron. The displacement of iron shows it is a less reactive metal than aluminium. This reaction is used as a source of molten iron for welding railway track.
