This practical shows pupils the differences between mixtures and compounds. In this example, a small amount of powdered iron and sulfur is mixed together in an ignition tube (not more than a quarter full). This mixture can easily be separated using a magnet because there are no chemical bonds between the two elements.
The mixture is then gently heated above a Bunsen burner until the mixture glows slightly. It is then removed from the flame for a few seconds and then reheated for a bit longer. It is left to cool.
The mixture will have turned into the compound iron sulfide and now cannot easily be separated into its former elements. The compound now has chemical bonds between the two elements and is no longer magnetic.
Equipment required (per set):
- Ignition tube
- Bunsen burner
- Heatproof mat
- Sulphur powder
- Iron filings