Chromatography Investigation

Here is my chromatography investigation!

Title: Using chromatography to identify pigments in green leaves and non-green leaves

Purpose: To analyze color bands created by chromatography to compare pigments within green and non green leaves in order to see what pigments are able to move further across chromatography paper..

Background: Plants use photosynthesis to produce sugars that the plants can use for energy to grow and to perform photosynthesis. Photosynthesis requires light energy in the form of photons to be absorbed by pigments. Certain pigments reflect some light wavelengths and absorb others, and the absorption of these light photons excites electrons and allows photosynthesis to happen. One pigment that appears in many organisms that perform photosynthesis is chlorophyll, which absorbs all light colors except green, which is reflected. Chromatography is a method used to separate compounds in a mixture by putting samples of a mixture on a strip of paper and putting one end of the paper in a solution. The solution travels up the paper strip because of diffusion. Some pigments in the mixture are more attracted to the solution than the paper and so travel up the paper with the solution. Some pigments are more attracted to the paper and don’t travel with the solution. Chromatography separates the pigments from each other and allows the pigments in the mixture to be identified to compare their Rf values. 

Hypothesis: If samples from a green leaf and a yellow leaf on chromatography paper are placed in an acetone solution, then the ratio of distance traveled by chlorophyll to the distance that the solute traveled will be higher than the ratio of the distance traveled by any other pigment to the distance the solute traveled. 

Data: 

Rf of pigment in green leaf: 0.94

7.4-1.4/7.8-1.4 = 6.0/6.4 = 0.94

Rf of pigment in yellow leaf: 0.98

6.8-1.5/6.9-1.5 = 5.3/5.4 = 0.98

Questions:

1. What is the basic importance of chromatography?

The importance of chromatography is to be able to identify different compounds within a mixture.

2. What factors allow chromatography to happen?

Chromatography is possible because of the different electronegativities of the compounds in the mixture. Each compound is attracted to the solvent and paper in varying levels, allowing the compounds to separate as the solvent moves through the paper by diffusion. 

3. What purpose does the chromatography paper have in this experiment?

In this experiment, the chromatography paper shows how far different pigments in leaves travel and shows the separation of the pigments. The paper gives a space for the solvent to travel and displays the different pigments as they separate. Since some pigments are more attracted to the paper than the solvent, the paper keeps those pigments in place.

4. What is the purpose of the solvent?

In this experiment, the purpose of the solvent is to move up the chromatography paper by diffusion and move pigments that are attracted to the solvent up the paper.

5. What does Rf value stand for?

The Rf value is the ratio of distance traveled by a substance to the distance traveled by the solvent. 

6. How do you think that the Rf value is useful to scientists?

The Rf value can be used to identify what compounds are separated from a mixture in chromatography. Scientists can compare Rf values to determine the identity of a compound.

7. What does Dunknown signify?

Dunknown signifies the distance that the solute or mixture traveled from the original marking on the chromatography paper.

8. What does Dsolvent signify?

Dsolvent signifies the distance that the solvent traveled from the original marking on the chromatography paper. 

9. How many pigments were you able to identify from the GREEN leaf chromatogram (Include a picture)?

Only one pigment could be identified from the green leaf chromatogram. 

10. How did a green leaf chromatogram compare to a non-green leaf chromatogram?

The green leaf chromatogram had very clear and visible bands of green pigment, while the non-green leaf chromatogram had more faint bands of yellow pigment.

11. What else did you find out about pigments and photosynthesis?

Different pigments absorb different colors of light. Chlorophyll absorbs red and blue light while reflecting green light. Therefore, chlorophyll is efficient in absorbing light to get energy for photosynthesis, because it absorbs two wavelengths of light.

12. What is one more question you have?

How much more or less efficient are other pigments than chlorophyll in absorbing light energy?

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