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Outreach: chromatography, how black is a black pen?

Description

Inside many black pens is a rainbow of colour trying to get out. Black ink is often made from a blend of other colours. In this activity you can try out paper chromatography to separate this mixture of inks.

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Inside many black pens is a rainbow of colour trying to get out. Black ink is often made from a blend of other colours. In this activity you can try out paper chromatography to separate this mixture of inks.

ADDITIONAL INFORMATION

Inside many black pens is a rainbow of colour trying to get out. Black ink is often made from a blend of other colours. In this activity you can try out paper chromatography to separate this mixture of inks.

This activity was demonstrated by the RSC at the Big Bang Fair 2014, and is a featured resource in our autumn 2015 'Get colourful with chemistry' theme.

If you teach primary science, click the headings below to find out how to use this resource:

Skill development

Children will develop their working scientifically skills by:

  • Using appropriate scientific language and ideas to explain, evaluate and communicate their methods and findings.
  • Drawing conclusions and raising further questions that could be investigated, based on their data and observations.
  • Asking their own questions about scientific phenomena.

Learning outcomes

Children will:

  • Use knowledge of solids, liquids and gases to decide how mixtures might be separated.
  • Compare and group together everyday materials on the basis of their properties, including their solubility.

Concepts supported

Children will learn:

  • That certain colours and dyes are made up from a mixture of colours and these can be separated by using techniques such as chromatography.

Suggested activity use

This activity could be used with a whole class with children working in small groups, investigating how to separate colours. They could start by investigating a black pen and could then move to look at different coloured pens and sweets and observing the results closely.

Practical considerations

You may need to experiment with a range of black pens beforehand, as some pens work better than others.

Filter paper will be required as certain papers are not absorbent enough to separate the colours out effectively.