Lesson Plan: Chromatography

A Science Investigation into the Different Colours that Make Black

Feb 28, 2008 Elizabeth Pace

Black ink is made up of different dyes and this experiment will simply demonstrate the separate colours.

Even though the ink from different black markers look the same when you write with them, they are usually made up of many different dye combinations. With this simple experiment you can separate the different colours and compare the results between different pens in a colourful, graphic way.

Aims:

To discuss colour mixing and black as a colour
To introduce a form of graphic recording
To conduct a scientific investigation
To practice some principals of fair and accurate testing
To encourage language through discussion

Materials:

Assortment of black felt-tip markers
Circles of blotting paper (or coffee filter paper) with a tongue cut out -the diameter needs to be larger than that of the top of the beakers
As many beakers as pens
Enough water to half fill the beakers
Paper
Magnifying glasses
Colouring pencils

Activity:

Start with a discussion about mixing colours to make new colours. Use the example of painting and creating colours and shades. Turn the discussion around how to create secondary colours and the idea of colour mixing.
Ask the students whether black is a colour or can you make black by mixing other colours?”
Introduce your activity by having a selection of black marker pens and get the students to draw marks on a plain piece of paper. Have them look closely at the marks to see if they can see any colours other than black. Maybe use a magnifying glass for this.
Introduce the various pieces of equipment and talk about making the experiment a fair test.
Have the students half fill each of the beakers with water
Have the students colour in a large dot in the middle of each circle of blotting paper with the markers. Make sure to use one pen per circle of blotting paper. The blotting paper is then placed on the beaker with the “tongue” just hanging in the water. Put the pens beside the appropriate beaker so you know which pen made which mark to keep the test clear.
The students watch as the water travels up the blotting paper as it is absorbed to the black dots. They then observe the different colours separate and spread.
In the form of a graph the students record which pen was used and which colours appear and in what order.
When the experiment is finished and the results are recorded let the blotting paper discs dry and then they can be added to the graphs.

Extension:

Is there a difference between the results when you use dry erase markers, washable markers and permanent markers?
Try this investigation with different coloured markers.

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Display the Results on a Graph