Monday, July 8, 2013

"Who Dunnit?" - Chromatography

This was one of the "experiments that the girls did in the forensic workshop. The Fashionista just loved doing this one and determining who the culprit was. She worked with Agent Smelly and they did get it tight ... yeah!

Chromatography is the process of separating small amounts of substances from a mixture by the rates by the rates at which they travel through a medium. Ink is a mixture of coloured dyes, so chromatography can be used to separate the mixture of dyes. 

The tutor pretended that she had just received a call from the police saying that they had received a bomb threat at the local supermarket and that they needed the children's help to work out "who dunnit?"

She held up the note with the threat on it and the bomber had used a black marker to fix one of the words on their typed bomb threat ... did my heart warm to know that we had a grammar conscious bomber.

Apparently 5 suspects had been detained with black markers, which were all different. It was up to the kids to determine which black marker wrote that letter so they could determine the culprit and stop the bomb going off. They had 30 minutes!

Each group of two children were given a test tube rack with 5 test tubes, 5 long strips of paper, some methylated spirits and water and a strip of paper, that had already been tested and matched the marker used on the note (similar to one of those pictured below).

There were 5 different markers, all numbered. The children placed one dot from each marker on each of their strips, about 2cm from the bottom, and wrote the corresponding number on the top of the strip.

The Girls Samples
(Should have written down what type of marker 140 was, it didn't run at all!)

They then placed 10 drops of the methylated spirits and 10 drops of the water in each test tube and then placed one strip of paper in each of them. Then they waited ... and waited ... and waited ... they worked on something else in the meantime.

The strips absorbed the liquid and slowly the dots started to change and in most cases run. The children then matched their strips to the strips of evidence they had been given and (well most of them) determined that it was marker 131 ... IE the supermarket butcher was the culprit.

Apparently said butcher had gone vegetarian a few weeks back and now hated his job so much that he wanted to blow the place up!


  1. Lisa, I used to work in a reasearch lab. I remember doing chromatography! What a great way to learn science. A vegetarian butcher? Someone's got a wild imagination!

    1. It was a bit of fun. That's interesting that you worked in a research lab.

      Yes The Fashionista found that bit to be hysterically funny!

  2. What a cool experiment. I was hoping to get the girls to do that detective lapbook this week (yeah I know I printed it out forever ago) and this would tie in nicely. Did you use plain printer paper? I might have to modify it a little as we don't have any test tubes.

  3. I think the paper needs to be pretty absorbant. I think we used that thicker absorbant paper that you use for water colours. Filter paper would work really well too.

    I am putting a package together, with that detective lapbook to do over the school break. I found some cheap "spy" stuff at the $2 shop ... should keep them out of trouble if they are looking for something to do.


Pin It