Page 7 - Curriculum Visions Dynamic Book

 After a while a number of changes have occurred because the iron filings have reacted with the copper sulphate. There is no acid or other chemical here.
Notice how the solution has become a very pale green. The edges of the iron filings have changed to a reddish-brown (coppery) colour, looking a little like a reef fringing a coral island.
The reason for the changes is that a chemical reaction has occurred. Some of the iron has gone into solution. The copper “reef” has been deposited (precipitated) out of the solution onto the iron filings.
The copper in the copper sulphate makes the solution blue; iron sulphate solutions are green, so the green colour shows that the copper and iron have “swapped”, and the solution is now iron sulphate.
However, not all of the iron has reacted. There is far more iron than copper, so a complete swap cannot be achieved. If the iron were placed in a huge vat of copper sulphate it would eventually react entirely
and disappear.
Also...
This demonstration
uses iron filings, the kind
of “swarf ” that might be produced as waste from
a metal lathe. If a large
mass of iron is present as
iron filings, there is a larger surface area than if
it were present in a large block. As a result, chemical reactions will happen more quickly.
cathodic protection: the technique of making
the object that is to be protected from corrosion into the cathode of a cell. For example, a material, such as steel, is protected by coupling it with a more reactive metal, such as magnesium. Steel forms the cathode and magnesium the anode. Zinc protects steel in the same way.
corrosion: the slow decay of a substance resulting from contact with gases and liquids in the environment. The term is often applied to metals. Rust is the corrosion of iron.
reactivity: the tendency of a substance to react with other substances. The term is most widely used in comparing the reactivity of metals. Metals are arranged in a reactivity series.
solution: a mixture of a liquid and at least one other substance (e.g. salt water). Mixtures can be separated out by physical means, for example by evaporation and cooling.
EQUATION: Reaction between iron and copper sulphate
Iron + copper sulphate ➪ iron sulphate + copper Fe(s) + CuSO4(aq) ➪ FeSO4(aq) + Cu(s)
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