Supplies Needed:
Small plastic cups or glasses
Paper towels
Food coloring in primary colors (red, blue, yellow)
Water
Questions to ask throughout the experiment:
What do you think will happen to the water?
What is happening now?
Why do you think the colors are changing?
Why might the water be able to move up against gravity like that?
Steps:
Place 7 cups in a circle and pour water in the 1st, 3rd, 5th, and 7th cups. The cups should be filled 3/4 up.
Add 5 drops of red food coloring to the 1st cup and the 7th cup.
Add 5 drops of yellow food coloring to the 3rd cup.
Add 5 drops of blue food coloring to the 5th cup.
Take a half sheet of paper towel and fold it in half lengthwise and in half again lengthwise.
Place one half of a folded paper towel in the 1st cup and place the other half in the cup next to it. Continue doing this until you have placed the last paper towel from the 6th cup to the 7th cup.
Observe the cups to see what starts happening. You should quickly be able to see the colored water begin to crawl up the paper towel.
Keep checking. Soon you will be able to see that the water has crawled all the way up the paper towel and is beginning to walk back down into the empty cup next to it.
Since the cup on either side of an empty cup has colored water in it, the two colors begin to mix in the empty cup.
How does it work?
The water travels up the paper towels through a process called capillary action. The paper towel is made from fibers and the water moves through the gaps in the fibers.
The gaps in the paper towel act like capillary tubes and pull the water upward. This is what helps water climb from a plant’s roots to the leaves at the top of the plant or tree.
The water is able to move upward against gravity because of the attractive forces between the water and the fibers in the paper towel.
Notes
We tried the experiments a few ways. One is described as above, the other was using three cups to make a more direct line to color. The colors were mixed on the paper towels instead of in the cups.
In addition to the previous learning concepts mentioned, you can also go through the steps of a science experiment. I work with a group of second graders. We did a before, during and after instead of defining the hypothesis, prediction, etc.
I let the kids draw what they saw and describe the various setups to the class.
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