Year 7 – Separating a Mixture

Last lesson the Year 7 students were given a mixture of salt, sand, iron filings and rice. Their task was to separate the mixture into it’s components, trying to conserve as much of the material as possible. This is the slideshow that previous year’s students prepared, showing how they went about the task.

Chromotography with Smarties and Autumn leaves


Chromotography  is a collective term for a set of laboratory techniques used to separate mixtures. It includes paper chromotography, thin-layer chromotography and gas chromotography. Paper chromotography is used for separating mixtures such as inks and dyes. In our practical experiment, we will use the natural food  dyes used to colour “Smarties”, although the artificial colouring used for “M and M’s” work well too. This is also a great time of year to investigate the pigments in autumn leaves – as chlorophyll breaks down to produce xanthophyll, carotene and anthocyanin. Another experimental method for leaf chromotography here.

Why do some trees have leaves that change colour in the autumn? How is chromotography used by forensic scientists and in industry? Please do some research and post your answers in the comments section below.