Rookie Science: Chromatography

Kids Club

Video Transcript:

Hi. My name is Rene. I am a children’s services staff member with the Charlotte Mecklenburg Library. And today we’re going to be trying a science experiment that’s called chromatography.

Now, chromatography is a process by which you separate out the components of a mixture. Now today, we’re going to be doing our test using magic markers.
Take a quick look here. Which color did I choose for my marker sets? Black. Now, I’m sure you’ve mixed paints before. And you know that if you mix red and yellow, you’ll get? Orange. If you mix red and blue, you’ll get? Purple. What colors would you mix if you wanted to make black?

Now today we’re going to try to figure out what colors the manufacturers of these markers mixed together in order to make their black ink. And the process we’re going to use is paper towel chromatography. Now here’s how chromatography works:

We’re going to be using an absorbent material—just some strips of regular paper towel. What we’re going to do is to make a mark on the bottom of the paper towel just like this. Now we’re going to use our cup to hold our paper towel in place, and we’re going to add a solvent. Something that will break apart the colors in that black ink. Since we’re using regular washable markers, we know that this color will dissolve in water. So I’m going to add just a little bit of water into the bottom of the cup just so that it touches the very bottom of the paper towel. Since the paper towel is absorbent, it will begin to soak up that water, and we’ll see it travel across the mark that we made with our marker. And it’ll begin to pick up and carry some of the different color components that are in that ink.

Now, I want to repeat this with my other markers. We want to figure out what colors were used to make this ink, but I’d also like to find out if every magic marker manufacturer uses the same secret recipe. So, let’s try it again with our second marker. I’m just going to make a mark at the bottom of the paper towel. Place it in the cup, just so it hangs over the edge. Clip it in place. And we’ll add some water. Just to the bottom of the paper towel so that it begins to absorb that liquid. And finally our last marker. Notice that we’re repeating the process exactly the same way with all three markers. Now this process does take just a minute or so as the water travels up the paper towel, but you’re already beginning to see some of the color in the ones that we started first. Let’s take a look at what’s happening with the first marker that we tested. I can already see some of the color bands showing up in this one.

Were your predictions correct about what colors were mixed together to make black ink? In this case, I can see a little bit of dark blue, almost a dark purple color, a little bit of brown, and maybe a little bit of pink as well. Now let’s take a look at the second marker that we tested. This one has a very different color pattern. In this one, I can see a little bit of an orange. Maybe even a bit of brown and a lot of turquoise—that’s a surprise for me! And finally, let’s look at the last marker that we tested. This one has a lot of colors that we can see. From the dark brown that’s at the bottom to the pinkish red in the middle, dark blue, and turquoise. There were a lot of colors in this blend! Now with this one, I also notice that the color bands stretch all the way from the bottom where we first put our mark all the way up to the very top where the water has reached.

And that is because each of the different colors that were used in this secret recipe have a different molecule weight. The heavier the molecule of color, the closer it is to the bottom. It doesn’t get carried as far up the strip of paper. The further up to the top it is, the lighter the color molecule. So it gets carried all the way up to the top by the water. Now that we’ve tried this chromatography process with the black magic markers, I bet you’re curious about the purple marker, or the green marker, or maybe even the brown marker that’s in your set. This is a very easy process to repeat with all of those other markers. I think you’re ready now to try your own chromatography experiments! Thanks for trying this one with me.

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