Name : ______Period: ______Date: ______
Methods of Separating Mixtures (Paper Chromatography, Centrifuge, Evaporation)
Purpose: The purpose of this lab activity is to observe how chromatography, the use of centrifuge and evaporation techniques are used to separate mixtures of chemical substances.
GLO’s: ______
HOM’s: ______
Introduction: Chromatography serves as a tool for the examination and separation of mixtures of chemical substances. Chromatography is using a flow of solvent or gas to cause the components of a mixture to migrate differently from a narrow starting point in a specific medium (filter paper). It is used for the purification and isolation of various substances. A chromatographically pure substance is the result of the separation.
Chromatography is also used to compare and describe chemical substances. In all chromatographic separations, there is an important relationship between the solvent, the chromatography paper, and the mixture. For a particular mixture, the solvent and the paper must be selected carefully to be able to separate the components of the mixture. For the solvent, it must be able to dissolve the mixture needing to be separated.
I. Problem: How do you separate the different components of black ink pens?
II. Hypothesis:
III. Experiment:
A. Materials: filter paper, pencil, test tube, rubber stopper, paper clip, metric ruler, black ink pens
B. Procedure:
1. Bend a paper clip so that it is straight with a hook on one end. Then push the straight end of the paper clip into the bottom of the rubber stopper.
2. On the line of your filter paper, put a “dot” using black in pen in the middle.
3. Hang a thin strip of filter paper on the hooked end of the filter paper.
4. Pour about 2mL of chromatogram solvent into the test tube.
5. Insert the filter paper into the test tube. (But before you insert the paper inside the tube, Make sure that the paper does NOT touch the side of the test tube. Also make sure that the “dot” from black ink pen will reach the solvent (liquid) at the bottom of the test tube.
6. Observe what happens as the chromatogram solvent (liquid) travels up the paper. Record the changes you observe.
7. When the solvent almost reach the top of the paper, remove the paper and mark how far the solvent traveled before the strip dries.
8. Observe your filter paper and identify the different colors that you separated. Then measure (using ruler in mm) the distance that different colors traveled in your filter paper.
Calculate the ratio for each color (Rf) by dividing the distance the color traveled by the distance the solvent traveled.
Rf = distance the color traveled
Distance the solvent traveled
Data Table:
Brand of Black Ink Pen: ______
Color of Ink / Distance each color traveled (mm) / Distance solvent traveled (mm) / Ratio Traveled (Rf)Bar Graph. Ratio Traveled (Rf) for each color
Discussion: (Please answer in complete sentences to receive full credit).
1.) How many colors are separated by your brand of black ink?
2.) What served as the solvent for your ink? As the solvent traveled up the paper, which color of ink appeared first?
3.) List the colors in order, from top to bottom, which separated from the black ink.
4.) In millimeters, how far did the solvent travel?
5.) From your results, what can you conclude is true about black ink?
6.) Why did the inks separate?
7.) Why did some colors of the ink move a greater distance?
8.) Explain the process and results of doing centrifuge, evaporation, and distillation in the lab. Describe what type of mixtures you have in the beginning and explain what happened to the mixture after you did centrifuge, evaporation and distillation techniques.
Conclusion:
Reflection:
1. What did you understand about this activity?
2. Which part of this lab is easy?
3. Which part of this lab is difficult to do or understand?
4. What is/are your questions for this lab or the lesson?