Fill the glass with water. How much water? Put the straw in the glass, and fill with water about 2-cm above it.
Add some food coloring.
Fold the tissue paper into the shape of a fan so that one end is open and the other is closed.
Compress the “stem” end of your flower and insert it through the end of the straw you cut in Step 1.
Put the straw-flower in the water and wait for a few moments – until the fan starts to change color.
If you’d like a multi-colored fan, transfer the straw between several glasses of water with different food colorings.
What’s the science behind this?
Water molecules (as well as molecules of other liquids) have a curious quality – they always want to stick together AND to the fibers of other materials, such as fibers of the tissue paper.
In our experiment, the water molecules stick to the fibers of the tissue paper and try to “advance” along them. The advancing molecules of water gradually color the paper as they climb up.
How does the water climb up, defying gravity? This happens because of the strong bond between the water molecules and the paper fibers, an attraction that only grows stronger as the water’s surface area increases and the paper fibers grow thinner. This gravity defying force is called capillary action - and it’s what pushes water up the root of a tree, along the branches, and to the leaves at the very top.
Capillary action can be found in other places, such as a kerosene lamp or candle that “pumps” the kerosene up the wick like a capillary tube. It is also capillary action that allows the tear ducts in our eyes to release tear fluid.
Now, try this!
Cut the painted flowers (draw your own flowers, if you like), fold the petals towards the center and gently place the folded flower over a bowl or glass filled with water. Make sure that the folded petals are facing up.
Now watch: What is happening to the flower?
Paper is made of fibers that look like tiny tubes. Thanks to capillary action, water climbs up the tubes, making them swell and expand. The expansion of the fibers causes the flower petals to open up.