A visible reduction

The reduction of copper oxide is one of the most common practicals used when introducing redox reactions and their applications in the extraction of metals. Often this will involve students heating copper oxide in a boiling tube or crucible in the presence of carbon powder. The result is often underwhelming and students can fail to see the colour of any copper they produce among the carbon.

A more reliable demonstration uses hydrogen as the reducing agent: it does not mask the colour of the copper that is produced and it has the additional advantage that the oxidation product is visible as condensation. However, the large scale version of this demonstration has a reputation for causing explosions when hydrogen/air mixtures form inside the tube. The following is a description of a smaller scale demonstration adapted by Bob Worley at CLEAPSS from one developed by Bruce Mattson at Creighton University, US. It works just as well and is far safer.

The glow of the reaction and the condensation are easily seen. The students are able to observe the formation of copper (it often creates an attractive mirror on the glass) and the safer demonstration means you can free up more of your mind to communicate with the class.

This demonstration would lend itself to any topics involving redox or metal extraction.

With an accompanying video, Declan Fleming shows how to set up, demonstrate, and adapt an experiment on microscale reduction of copper oxide.