Investigation 3:

Color Writing

Mrs. Tweedie

September 2010

Part 1: Making Chromatograms

Once upon a time a scientist was writing a letter to a friend when a curious thing happened. While he was out of the room for a few minutes, a gust of wind from the open window blew his unfinished letter across his desk and a corner of the letter dipped into his cup of tea.

Part 1A: Making Chromatograms

When the unlucky scientist returned to finish his letter, he was amazed by what he saw. His letter was unreadable, but he made an important discovery. We can repeat his experience to find out what he discovered.

Part 1A: Making Chromatograms

Teacher Demonstration

1. Use a purple pen to write a word across the width of the strip 2 cm from one end.

2. Put 1 rubber bands around the basin to make a clothesline over the open basin.

3. Lower the strip, ink end down into the basin right next to one of the rubber bands. When the tip of the paper (not the ink) just touches the water, you should fold the paper over the rubber band so that it will hang at that level. Use a bobby pin to secure the paper to the rubber band.

word

Part 1A: Making Chromatograms

Your Turn

1. Get a basin and 1 rubber bands for your group.

2. Get water for your group.

3. Get a purple marker and one strip for your group. Prepare the strip.

4. Attach the strip. If the word touches the water, the investigation will have to be started over.

word

Part 1A: Making Chromatograms

What did you observe?

Part 1A: Making Chromatograms

The color in the ink is called pigment.

Part 1A: Making Chromatograms

The process by which pigments are made to move using paper and water is chromatography. The finished product of chromatography is a chromatogram. A chromatogram is a color record.

Part 1B: Making Chromatograms

Today we are going to make chromatograms. You can use this sheet to record the results of several chromatography investigations. Set up the basin with 4 rubber bands and water.

Part 1B: Making Chromatograms

1. Select a colored pen. Make a mark (line) in the color box at the top of one column on the record sheet.

Part 1B: Making Chromatograms

2. Each team member will use the same pen to draw two lines on a filter-paper strip, 2 cm from each end of the strip.

3. Hang the strips from one of the rubber bands for about 3 minutes.

4. Remove the completed chromatogram from the rubber band and blot it dry. (Place the strip between two paper towels and press gently to soak up excess water.)

Part 1B: Making Chromatograms

5. Tape the chromatogram to the student sheet in the proper column.

Part 1B: Making Chromatograms

6. Make eight chromatograms, one for each pen. Tape chromatogram to your record sheet.

Vocabulary

Chromatographyuses water to carry pigments from one place to another.

ChromatogramThe product of chromatography.

PigmentA colored chemical. Watercolor pens have pigments.

Part 2: Mystery Pen

I need your help in finding the mystery pen described on the wanted poster. I have four possible pens that could be the mystery pen.

Part 2: Mystery Pen

Use the color-writing technique and compare the chromatograms from each of the four pens to the mystery pen.

Part 3: Content Inquiry

What can you see with chromatography that you couldn’t see before?

Part 3: Chromatography Inventions

Use chromatography to make an animal or tree.