Inside: We explored five different ways to do chromatography experiments in our kitchen. They are a colorful combination of science and art, and are easy to do at home using ordinary items: food coloring, candy sprinkles, essential oils, and markers.
Disclaimer: Last week our marker chromatography experiment didn’t go as usual. Instead of separating as they are supposed to, the colors simply spread uniformly down the paper.
“Your experiments always fail,” announced my oldest son with a grin. Thanks, kid!
I’m blaming the new, fancier (read: more expensive) brand of markers we used. Still, it looked pretty and, judging from my other kids’ excitement, was not altogether disappointing.
I’m mentioning this fail just in case your experiments – line mine – don’t always go the way they are described. If your kids complain, just shrug and tell them that learning how to handle failure is part of the scientific life.
The Discovery of Chromatography
Chromatography, or “color writing” from the Greek chroma “color” and graph “to write,” is the science of separating mixtures. We also refer to it simply as Tsvet’s science, after the Russian scientist who discovered the technique and coined the term “chromatography.”
Mikhail Tsvet (by the way, “tsvet” is actually a Russian word for “color” – Coincidence?) discovered that since different color pigments have different weights, they are carried along at different speeds, and end up in different places. So one can use different substances (gas or liquid) to carry the color, and by examining where different tints end, figure out what pigments were combined to make it.
Chromatography is now widely used in biochemistry to figure out the ingredients that make up a particular scent or flavor, to detect traces of drugs in urine, and to find traces of pollutants in drinking water.
Too bad that Tsvet’s work was largely unknown (due to it being in the Russian language) until years after his death. Today his gravestone carries the inscription: “separating molecules, uniting people.”
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What is Chromatography?
To make it easier for kids to grasp the concept of chromatography, I started by asking my kids to imagine themselves in a forest. Everywhere they look, trees are stretching toward the sky like towers. The twigs crunch under their feet. Small animals scurry around in the underbrush.
And now, as if by magic, a toy box drops down from the air in front of you. In the box, there are light toys (balls, dolls, and books) and heavy toys (ride on trucks, giant Barbie house, and a LEGO table). Suddenly, though, a flood sweeps through the forest.
You are ok! You climbed a nearby tree. But the contents of the box are scattered all over the forest floor.
Would all toys travel the same way? Would it be as easy for water to sweep the LEGO table through the forest it is a beach ball?
Would scientists be able to make educated guesses about the weight of different toys by examining how far they traveled? Yes, they could!
Chromatography is a science that studies the components of a mixture (toys in a toy box) and tries to figure out things about them by studying how far they traveled.
Chromatography Experiment with Markers
Markers in a variety of colors
Glasses with water
What to do
- Cut paper towels into long strips about an inch wide.
- Draw a heavy line with a marker near the top of one stripe (black is often a fascinating color that separates into bright blue, green, and yellow).
- Hang the paper strip over the edge of the glass of water so that the paper towel touches the water, but the line is above the water.
- Watch the color spread as the water travels up the paper.
The incredible thing is when seemingly “boring” colors (like black) separate into many unexpected colors!
How to Recycle the paper strips
If you are looking for a creative way to use up the strips used in this experiment, you can put them in a blender equipped with a S-blade, add a little water and turn it into a mush. If you then press the resulting mash into a cookie cutter and let it dry overnight, you end up with a beautiful 3D art. Read about our red heart for inspiration here.
Chromatography Experiment with Candy Sprinkles
paper towels (or coffee filters)
sprinkles of different colors
What to do
- Place sprinkles in the middle of paper towel
- Add water
We knew that in commercial food production, yellow and blue are usually made up of just one die each, so no surprise there. We didn’t expect much color separation.
However, what surprised us is the color red. We were amazed to see so much yellow in it.
My kids couldn’t resist adding a sensory element to the experiment and rubbing the mixture with their fingers.
- The paper towels are almost works of art in themselves. You might even have your kids arrange sprinkles artistically on the paper and then simply pour over water to see what beautiful patterns emerge. This is especially nice for very young kids, because no matter their grasp of fine motor skills, the end result will be beautiful.
- Try the same experiment with jelly beans or M&Ms.
Chromatography Experiment with Food Coloring
What you need
Food coloring in various colors
Sticks, popsicle sticks, or pencils
What to do
- Cut the paper towel in several strips just a bit taller than your cup.
- Add food coloring to an inch of water in a cup.
- Tape the strip to the stick, so that the bottom touches the liquid in the cup.
- Suspend the strips on top of the cups. Make sure that the paper touches the food coloring.
- Does the color separate into different colors as it creeps up?
It was interesting to see so much green coming out of black color (see the top of the paper). We thought it looked kind of like those pictures of nebulae in space.
It’s even more fun to mix many different colors of food coloring in one glass and see how they separate as they move up the paper towel strip. Just don’t add too much black food coloring because the strip gets too dark to detect any color separation.
Chromatography Experiment with Essential Oils
If you were ever interested in essential oils, the number one question that probably popped into your head was How can I trust that this essential oil is pure and not heavily diluted?
There are many different ways to check the quality of the essential oils in a laboratory setting, but what about at home? Don’t worry: there is one in-home testing method that is considered “fairly accurate.”
What you need
White (printing) paper
What to do
- Cut white paper into strips. One for each essential oil you are testing.
- Dispense a drop of essential oil on each paper strip.
- Allow to dry for 24 hours (It might take 48 hours for thick oils like Sandalwood to dry).
A pure essential oil should dry without leaving a stain.
Essential oils that have been diluted with synthetic fragrance oil will leave an oily residue on a piece of paper.
From ten oils we tested, only 2 failed the test. As you can see on a pic above, all the Kis oils passed the test, but my favorite rose oil didn’t pass the test, and neither did Sweet Orange from Aura Cacia (but Sweet Orange from Kis was fine).
The fun part of this experiment is that while we were testing all my different oils, our house smelled like an Essential Oils Shop. Science can be so calming.
Chromatography Experiment with Permanent Markers
In experiment #1 above, we used water to separate colors from markers, but this time we are tackling permanent markers. Permanent markers are water-insoluble (that’s what makes them permanent), so we know that water is not going to get the job done. We looked around the house and gathered up rubbing alcohol, nail polish remover, and vinegar to see if they will help us separate colors in permanent markers.
What you need
paper towel strips
permanent markers (the colors black and green were most interesting)
rubbing alcohol, nail polish remover, and vinegar
What to do
- Cut paper towel in strips.
- Draw a heavy line across the strip with a marker (or a couple of thin lines).
- Fill cups with a bit of the chemical you are testing out: vinegar, nail polish remover, or alcohol.
- Hang the paper strip over the edge of the glass so that the paper towel touches the liquid, but the line is above the liquid.
- What’s happening?
In our case, nail polish remover produced the most colorful results. We were pleasantly surprised to see so much blue in a black marker. Also, note the intense yellow color in a green marker strip.
And that’s five ways to do Chromatography Experiments with kids at home. If you are not doing them now, PIN this page for later.
More Chromatography Fun!!
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