In this activity, children explore how some materials repel water. They learn that some surfaces have unique properties that could be used for other real world applications such as self cleaning windows etc. The activity uses dried lotus leaves, which repel water very strongly. They are called superhydrophobic. Here is a lotus leaf in action!
What you’ll need
- Squares of;
- Regular paper
- Kitchen foil
- Kitchen roll – optional
- Plastic (foodbags/wallets etc)
- “Dirt” – chocolate powder (clipper chocolate powder works well)
- may require dairy free equivalent if someone has dairy allergy
- Lotus leaves (you can buy a pack of dried lotus leaves for about £5 online e.g. at souschef.co.uk)
- Cups of water
- Plastic pipettes
- Plastic trays
To prepare in advance
Set up “activity trays” so a tray has everything that a pair of children would need. This would include a cup of water for the children to share, squares of each material (roughly the size of a drinks coaster) and small cup of “dirt” (chocolate powder) i.e. so there is enough for child to sprinkle on each material.
Get the children to sprinkle a bit of “dirt” onto a material (better to start with paper and finish with lotus leaf). Then get them to pipette water droplets onto the surface of the material and see if they can move the droplets about to try and remove the dirt. You can then get them to write an observation/compare observations for each material on what happens to the droplets and how easy/difficult is it to remove the dirt from the surface. It should be obvious how difficult it is to remove the “dirt” from materials such as paper, but the lotus leaf should have droplets form on the leaf surface collecting the “dirt” as the droplets move across the surface.
Tip; It is useful to perform the activity in the tray to try and minimise mess!
At the end of the activity you can discuss with the children how the lotus leaf acts as a self cleaning material, to remove unwanted dirt and germs from its surface. You can then get the children to suggest real world applications of self cleaning surfaces such as windows etc.
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