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Chromatography with Autumn Leaves

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Introduction

Chromatography with Autumn Leaves Chromatography is used to separate pure substances from a mixture of substances, such as a cell extract. It is based on various substances having different solubility's in several solvents. The components that are separated are distributed between two phases: a stationary phase and a mobile phase. This technique separates the substances in terms of the relative size of the molecules. We used this technique to identify the pigments present in autumn leaves. The function of a plants pigment is to trap light energy and convert it into chemical energy that can be used by the plant to make glucose and sugar. The leaves change colour in Autumn because the chlorophyll starts to break down to allow the other plant pigments colours to show, these pigments in clued the red, yellow and orange. There are four main types of chromatography. These are Liquid Chromatography, Gas Chromatography, Thin-Layer Chromatography and Paper Chromatography (which we used). TLC (Thin Layer Chromatography) ...read more.

Middle

We used Paper Chromatography the method is outlined below. > A spot of the substance (crushed leaves and ethanol) is left on the chromatography paper left to dry. > Once dried another spot is added on top then the paper is suspended in a solvent which in this case was ethanol. > As the solvent molecules move through the paper the components move up the paper. > The substance eventually separates out into different spots. Safety Precautions All solutions should be disposed of in the liquid waste container. All solids should be disposed of in the solid waste container. Chromatography works when the solvent rises up the chromatography paper. When the solvent reaches the "spot" it dissolves the mixture of coloured chemicals. This is when a solution is formed. The mixture of solutes dissolves in the solvent. The molecules of these different chemicals become all different sizes. During my experiment I observed this as I noticed that the big molecules moved slower than the small ones. ...read more.

Conclusion

From looking at my results I can see that my highest Rf value was 0.278 which indicates that it has the lowest molecular mass in the table. Evaluation Error Analysis The chromatography paper touched the sides of the tube-test during the waiting time which caused the movement to go slightly to the side instead of straight to the top. The strip was also a little bent at the top which could have been a slight error in measuring the movement of the solvent front. However I feel that these errors were insignificant and so my results are reliable. To correct these errors I could use some tweezers to slide the chromatography paper in the tube gently. For further study I would Research Location Name Purpose Websites www.biologymad.com www.mrothery.com www.newton.dep.al Helped me research background information on what the different types of chromatography are available. Books Letts As Biology revision Guide Helped me understand what the Rf values are and how they help (included in write up) Pete Ifrah Thabet Pg 1 ...read more.

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