Chlorophyll is the green pigment found in plant leaves. Chlorophyll absorbs sunlight and converts it into energy for the plant. Students can better understand chlorophyll by extracting it from leaves. This shows the students what the true color of the leaf is, which they can also see in autumn just before the leaves fall off trees.
Note: Always conduct this experiment with adult supervision and caution. Ethanol and other solvents are extremely flammable. Do not conduct around open flames or heating elements.
Things You’ll Need:
- Leaves from corn plants (not husk) make an excellent chlorophyll source for any green
- Leaves will be ok such as fresh spinach
- 1l bucket
- 70% ethanol or 70% isopropanol (rubbing alcohol)
- Plastic holding containers with lids
- Disposable bo s wl
- Glitter of different colors
- Paint brushes
- Test tubes
- Small flashlight with bright illumination
- Paper hole punch
- Elmer’s all-purpose school glue or any other school
- 2 squirt bottles with 70%etoh, and water
(2 days) prior to exhibition
- Set bucket in a sink
- Fill a bucket with leaves
- Add ethanol (EtOH) to a bucket and let soak for 1 hour to allow chlorophyll to leach out of a leaf
- After 1 hour, pour off extract into holding container and close lid
- Repeat steps 1-3 until 1L of chlorophyll or the desired amount has been extracted
Note: Chlorophyll is a molecule, which breaks down within a couple of days after extraction, and the color gradually fades.
Morning of the exhibition:
Create work areas (stations) by blocking off areas on a 5×8’table:
- a. Station #1– demonstrate extraction
- i. using the hole punch take samples from the leaf and place in a Petri dish
- ii. using a squirt bottle filled with EtOH, fill a dish with ethanol
- iii. as samples are cleared of chlorophyll transfer some to another dish with water for viewing at station 2
- iv. refresh dish (I) with newly punched samples
- b. Station #2– microscope viewing
- c. Station #3– properties of chlorophyll
- i. pour some of the extracted chlorophyll into test tubes and seal with a cap
- d. Station #4– painting with chlorophyll
- i. Add approximately 2 tablespoons to disposable bowls and mix enough extracted chlorophyll so that the glue “thins” and becomes more like paint
- ii. Add a little glitter
- iii. Repeat steps 2-3 for different glitter colors
Note: Station #4 is for creative freedom. The chlorophyll paint can be used to paint trees, flowers, etc. For more of a sparkling effect, add glitter after painting as well.
Exercise #1- Chlorophyll Extraction:
Chlorophyll can be removed (extracted) from plants by soaking the leaves or chlorophyll-containing parts in an alcohol such as ethanol (EtOH).
- Pour 2 cups of water into a medium-sized pot and set it on the stove. Turn the heat setting to high.
- Bring the water to a boil and set your leaf in it for two minutes.
- Remove the pot from the heat. Use a slotted spoon to take the leaf out.
- Pour 1 cup of rubbing alcohol into a tall, heat-safe glass and set it in the middle of the pot of hot water. You don’t want the water from the pot to spill into the glass.
- Place the leaf in the glass with the rubbing alcohol. Make sure the leaf is entirely covered with rubbing alcohol.
- Wait one hour and return to check on the leaf. The leaf should now show its true color. The rubbing alcohol will now be green. The green in the rubbing alcohol is the removed chlorophyll.
Ethanol is an organic solvent that causes plant cells to become leaky. The chlorophyll inside the cells becomes available and dissolves in the ethanol.
Congratulations!!! You have just completed your very own chlorophyll extraction.
Go on to Exercise #2 to view your leaf sample under a microscope.
Exercise #2- View Leaf under Microscope:
Once the chlorophyll is removed (extracted) from a leaf sample, some parts of the leaf cell structure can easily be viewed under a microscope.
- Place a petri dish with leaf samples under a microscope and carefully focus to view your sample.
- Can you identify any of the parts in the diagram?
The epidermal cells of the corn leaf are visible. Epidermal cells allow respiration. Yes, plants breathe too. Plants breathe in carbon dioxide (CO2) and release oxygen (O2). Humans breathe O2 and release CO2.
Congratulations!!! You have just completed microscope training.
Go to Exercise #3 to learn more about chlorophyll.
Exercise #3- The Wonders of Chlorophyll:
Chlorophyll is visible as a green color. However, when white light is shined on extracted chlorophyll other colors become visible.
- Pick up a tube of chlorophyll (do not open).
- Shine the flashlight on the tube.
- What color(s) do you see? Red/violet
- Do you know why those colors are visible once the flashlight is shined on the chlorophyll?
Chlorophyll is a photoreceptor made up of two molecules: chlorophyll a, and chlorophyll b. As a photoreceptor, it absorbs light energy from a source such as a sun. Once captured, light energy breaks molecular bonds within the chloroplast and turns it into chemical energy that the plant needs to grow.
Light energy, measured in nanometers (nm), comes in different lengths. These wavelengths are part of the visible light spectrum which is actually a combination of different wavelengths from 700-400nm.
If separated, these wavelengths appear to humans as different colors: red (700-650nm), yellow (650- 600nm), green (600-500nm), and blue/violet(500-400nm). Chlorophyll has the unique ability to separate and absorb energy from some wavelengths and reflect others.
Chlorophyll is seen as green (600-500nm) because it does not absorb this color but reflects it. However, it absorbs quite well in the red-light spectrum (700-650nm). When chlorophyll is contained in the plant, it converts this to chemical energy so that the red light is not visible.
However, extraction stops this cycle when chlorophyll is removed from the plant and other components needed for this conversion. Therefore, instead of absorbing and converting the energy, it can only absorb and reflect it.
Congratulations!!! You have just completed Junior Scientist training.