When green is red

Take the green from green leaves!

Difficulty:
Danger:
Duration:
20 minutes

Reagents

Safety

  • Do not aim UV light at eyes or face.
  • Put on protective gloves and eyewear.
  • Conduct the experiment on the safety underlay.
  • Observe safety precautions when working with boiling water.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

Step-by-step instructions

How can you take the "green" out of a green leaf? First, you need to crush the leaf, because the "green" is contained deep within its structure, behind tough walls.

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The "green" in plant leaves is actually a set of similar chemical compounds called "chlorophylls." To separate them from the remainders of your leaf, you can just "lure" them into a liquid. Water is often a very good liquid for similar purposes. Chlorophylls, however, don’t approve. They prefer other kinds of liquids, like oils, alcohols, or triethyl citrate.

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The chlorophylls don’t migrate into triethyl citrate exceptionally fast, but you can speed them up by heating the mixture.

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You've got most of your leaf's "green" dissolved in your triethyl citrate! Isn't this liquid pretty green? Or is it? Take your UV light and shine it at your vial. This green is sometimes actually kind of red!

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Disposal

Please refer to local regulations when disposing of chemicals. Dispose of other solid waste with household garbage. Pour leftover solutions down the sink. Wash with an excess of water.

Scientific description

Your eyes aren’t deceiving you; chlorophylls are actually green. But why did you see red? When you shine regular white light on chlorophyll, you’re actually illuminating it with all the colors of the rainbow. That's because white light is really a mixture of all these colors. Red, green, blue, yellow, and violet all hit the solution at the same time. However, most of the blues and reds get stuck in it, and only the green portion of the light is able to pass through the liquid or bounce back into your eyes. Hence, you perceive the solution to be green.

The light from the UV flashlight, however, contains no green whatsoever. Conversely, it doesn’t contain any red, either; it consists of barely-visible blue/violet and invisible ultraviolet light. So the solution should look, if anything, violet—why does it look red instead? As it turns out, the light from the flashlight is absorbed by the chlorophyll, but it's not lost. In fact, the ultraviolet light causes tiny changes in the chlorophyll molecules, causing them to get "excited." They immediately change back, however, and in doing so, they release some light back. And this light happens to be red

Chlorophyll isn’t the only plant-based substance that behaves in such a manner. Curcumin, for instance, is also soluble in triethyl citrate and has a beautiful yellow-green glow to it!

That’s interesting!