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Whether we think about it or not,
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chemistry has always played a big role in art and culture.
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Just take colors for example!
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But what is a color really?
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And what led to the use of some colors in the first place?
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Let's trace a color back to its roots. And leaves.
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One color story started with this plant, called Indigofera tinctoria or Indigo.
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It's native to India and the name comes from the Greek work indicon,
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meaning Indian substance.
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Substance?
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In this plant there is a colorless molecule that looks like this.
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But under some conditions, this molecule can react and change,
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looking like this instead.
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So what's the big deal then you say?
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In chemistry, rearranging the molecular structure like this
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can be like night and day, or in this case like green and blue.
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Because this last molecule is blue.
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After its discovery, people now wanted the blue indigo molecule,
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especially for dying clothes.
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But this is where it gets a little tricky.
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You see, this blue indigo molecule is insoluble,
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meaning the blue dye simply won't stick.
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We now know that to overcome this, the solution that the dye is in has to have a high pH.
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Well, people did still figure this out a long time ago.
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So what did people have a few thousand years ago to raise the pH?
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Did you know that urine becomes basic over time?
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What is believed to have happened is that leaves from the indigo plant
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got accidentally soaked in urine.
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So if a textile came in contact with the basic urine-indigo solution
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it turned blue!
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So the high pH actually helped the molecules stick to the fabric.
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But wait a minute...
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How can this molecule be colorless and this be blue?
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Hey Louise, can you take it from here?
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On it!
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When we look at the two molecules again, we can see that the blue molecule is larger
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and has a greater number of double and single bonds.
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It is this molecular structure that ultimately makes us see the colors.
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But first we need light.
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Light contains wavelengths of all colors.
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If something is black, all the colors from the light are absorbed
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and none is reflected back to our eyes.
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We therefore see the object as black.
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Now if we look at something colorful,
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we see the red color because the flower reflects back the red wavelengths and absorbs others.
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And the reason the flower absorbs particular colors comes down to its chemical structures.
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So these alternating double and single bonds are the reason the indigo molecule is blue.
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And if certain atoms are added to the molecule the absorbed wavelengths can change,
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and that makes us see a different color.
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The discovery of indigo color was huge for ancient art and culture.
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And by understanding the chemistry behind it we can now synthesize the same molecule that
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was for so long extracted from this plant.
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And the use of indigo is still booming,
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in fact we use about 13 000 metric tonnes every year.
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And if we weren't synthesizing the molecule,
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we would have needed about 3.9 billion kilograms of plants per year.
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By the way, you might even be wearing some of it right now.
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So we've learned that the colors,
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that have an important role in art and culture, have some interesting chemistry histories to tell.
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And the reason we see colors in the first place comes down to the structure of the molecules.
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And just by changing the molecular structure slightly we can even change the color we see.
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And here's a challenge.
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Can you think of any other colors that have come from plants or animals?
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And remember,
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Chemistry is all around you!
