Chromotography: An Open Inquiry
This lab activity helps students start thinking in terms of the scientific process. After a short demonstration on chromatography, the students will brainstorm ways to make the experiment different. Students will also develop a new, testable question related to chromatography and write a procedure to gather data on their new question. From this process they will be able to draw conclusions about the experiment as a whole group.
1. This activity is designed for students to use critical thinking, experimental design and data analysis throughout a scientific investigation.
2. This activity is designed for students to use skills such as observation, questioning, laboratory techniques, and oral and written presentations.
Context for Use
Chromatography can be used in grades K-12. For the younger grades a simple demonstration can be shown for the visual learners. This can be easily done in one class period however, if you want to use it as part of an extension to scientific method it will take several class periods. Chromatography does not require any special equipment. Most of the equipment can be found in your storage cabinet. Since it is so easy, no special skills are require to be taught before the lesson.
Description and Teaching Materials
I am using this lesson to incorporate more inquiry in my lesson and to teach students to use the scientific method in their approach to solving questions. Since I will be teaching this lesson to fifth grade students, I expect them to be able to chose a variable and design an experiment that will solve their own question.
Materials needed for this activity include; water-based markers, filter paper, cups, pencils, tape, and water. Extra items to have for student driven experiments include; permanent markers (make sure they are not the primary colors), coffee filters, regular white copy paper, white construction paper, alcohol, and vinegar.
I intend to model the chromatography activity. To do this cut filter paper into strips approximately 1" wide. This will allow the students to get a good look and the inks in various markers.
- Ask the students, "What two colors make orange"
- At this age they should respond red and yellow.
- Ask the students, "How do we really know that there is red and yellow ink in the orange maker?"
Take all acceptable answers. Tell them that you are going to separate the orange ink into its two components to prove this hypothesis. Next draw a line across the filter paper approximately 1" above the bottom. For the demonstration use an orange water based marker. Then tape the filter paper to a pencil and hang it in the water so the filter paper is touching the water but that the mark is above the water level. Leave the filter paper in the water until the ink has been forced up the filter paper through capillary action. When the ink has separated out, take the filter paper out of the water and lay it on a clean piece of copy paper.
- Ask the students ,"Did the orange marker separate into the colors you thought."
Next ask them how they can change the experiment. At this point you should get several answers leading to many variables. Make a list of their responses on the board. When they have brain stormed as many answers as possible, tell them that they are going to repeat the experiment only they will chose one of their ideas off the board. Put the students into groups of four according to the variable they chose to test. At this point the students must write a hypothesis as to what they think will happen in their experiment. They must also plan and design an experiment to test their hypothesis.
At the end of the activity have all groups share their original hypothesis and results. Your questions will depend on the different variables that the students chose to test. They should have written a good hypothesis and procedure to test the hypotheses.
Teaching Notes and Tips
1. Since the students will decide how the experiment can be changed, be prepared to have several items on hand to accommodate the variables. However, my students will be limited to the everyday items that I keep on stock.
2. Whenever using solvents other than water make sure the students use goggles.
3. We have a no eating or drinking rule in the lab so this shouldn't be a problem but be prepared for anything.
4. The purpose of this experiment is to make sure the students use the scientific method to solve a question. Chromatography is easy but the purpose must be kept in mind.
Assessment for this activity will come from the student documented hypothesis and procedure recorded in their science journals. If they wrote a good procedure which tested the original hypothesis then their experiment should work as they planned. The end result is not the important part of this activity. Only assess their hypothesis and procedure to see if they used the scientific method to solve their question.
5.I.A.1 - Scientific Investigation
5.I.A.2 - Communication
5.I.B.1 - Controlled Experiment
5.I.B.2 - Scientific Investigation
References and Resources