Black marker chromatography. STEM session plan.
In black marker chromatography experiment, students will discover that a black marker is made of several different colour pigments, by making a chromatography investigation. Don’t worry, this is not a dangerous CSI investigation, just an exciting STEM activity suitable for primary school students.
Students should be able to explain what makes something a mixture.
Understand that mixtures can be separated into their components.
Use the process of chromatography to separate the pigments in black marker.
Chromatography is one of the most impressive techniques scientists use to separate mixtures and determine the ingredients mixtures are made of.
The name chromatography comes from the Greek words chroma and graph meaning “colour writing.” The technique was developed in 1910 by Russian botanist Mikhail Tsvet. He used it to separate the pigments that made up plant dyes.
Chromatography is used in many different industries and labs. For example, police and other investigators use chromatography to identify clues at a crime scene like blood, ink, or drugs (well, there is a bit of CSI after all!) .
- White paper towels
- A tall glass
- Black marker/s
- Cloth pin or binder clip
Carefully cut the paper towel into a strip. Using black marker, draw a line across the width of the paper strip, about a couple of centimetres from the bottom end.
Fix the paper strip next to the rim of the tall glass with the help of a cloth pin then slowly add water in the glass until the level just reaches the bottom end of the paper strip. It is important that the water level stays below the marker line on the strip. It will take two to three minutes to complete the experiment as the water rises up the paper strip.
When the water has climbed nearly the whole way to the top, take the strip out of the glass and lay it flat to dry. Look closely at the strip. Which pigments the black marker ink is made of?
What is happening? Most non-permanent markers use inks that are made of coloured pigments and water. The water in the ink carries the pigment onto the paper and when the water dries, the pigment stays on the paper.
When you dip the paper in water, the dried pigments dissolve. As the water travels up the paper, it carries the pigments along with it. Pigments are made up of molecules! Some of these colour molecules are smaller and lighter than others, so they move at different speeds. Since the water carries the different pigments at different rates, the black ink separates to reveal the colours that were mixed to make it.