Use liquid watercolors to motorize a leaf and explore the Marangoni effect. Take this experiment further and explore the differences between hot, cold, and room temperature water. Then explore how different leaves behave under these conditions. You could also try things like food color or ink and see how this affects the speed at which the leaf moves. This experiment has so many avenues of exploration and can be modified for all ages.
Supplies & Instructions
Bin or tray
Fill a bin/tray with water. Fold the leaf like a taco (do not crease). Add a few drops of liquid watercolors to the edge of the leaf, then gently set in the water. For kids, setup liquid watercolor in cups and use a dropper to add to the leaf. Once your leaves stop moving, it's time to change the water. Head to our Instagram account to see a video tutorial.
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How it works
This works, because the surface tension of the liquid watercolor is lower than that of water. This creates a gradient of lower surface tension to a region of higher surface tension when the two mix. This is called Marangoni flow. The force that results, causes the leaf to move forward. Why are my leaves not motorizing anymore? At some point, there will be enough liquid watercolor in your water that there won't be a great enough difference in surface tension anymore. This indicates it's time to change the water.
Preschool prompts: show this experiment in room temperature water. What do you think will happen when we try this in hot water? What about in cold water? Describe what happens. Do you think this experiment will work with other types of leaves? What happens when we change the color of the liquid watercolor?
critical thinking, basic science concepts, descriptive language development, color theory, fine motor development