This morning, my daughter and I got out some white coffee filters and started playing with liquid chromatography, which is defined as: a process in which a chemical mixture carried by a liquid is separated into components as a result of differential distribution of the solutes as they flow around or over a stationary liquid or solid phase.
In other words, you can use chromatography to separate pigments, or color molecules, using water (the solute) to carry them up a strip of coffee filter (the solid phase.) Different molecules travel at different speeds, so you can see some of the many colors contained in a black marker as the pigments race up the strip.
You’ll need white coffee filters, or paper towels, cut into strips just long enough to hang over a pencil or ruler that is balanced on the lip of a jar or cup without quite touching the bottom of the jar. We cut wider strips and hung them over a ruler balanced on two water glasses over a tupperware container. Look at the pictures and you’ll get the idea. You want the bottom of the paper just barely touching the water and not touching the sides of the container.
To see what colors are contained in different markers, draw dots about half an inch above the bottom of the paper and drape the paper over the pencil, just letting the bottom of the strip barely touch the water. You don’t want to submerge the marker dots. Let the water travel up to the top of the strip to see good separation. (See top photos.) Black and brown markers are especially interesting. Try several of them- they’re not all alike.
I was trying to think of a fun Halloween science experiment, so we came up with this variation on magic marker chromatography. Start by drawing faces with markers on the bottom of filter strips and hanging them over pencils on cups with the bottoms of the strip barely submerged in water at the bottom of the glass. The water will slowly travel up the paper, taking the pigment with it. It’s fun to watch the face blur and slowly disappear into line of color.
My daughter did this for an hour without getting bored. You can also do marker chromatography with thin strips of paper containing just one color or by dropping water on a dot you draw with a marker.
- Survival Science: Water Filters I demonstrated this experiment on Kare11. Click here to watch...
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