This was one of those experiments that was a real trial and error one. We have made many bugs out of several different materials. I was trying to be creative and use some bits from our recycling box but actually if I had just followed the instructions to start with and use good ol’ craft shop card then we would have achieved floating bugs on the first attempt!
What you need:
- Card (essential – definitely use proper card and not cereal boxes like we did!)
- Pen & scissors (essential)
- Bowl of water (essential – or can use bathroom/kitchen sink).
- Crayons & stickers (not essential – but good fun for decorating)
- Butter (not essential but good for doing a further experiment).
What to do:
- Fold a piece of card in half and then draw a big footed bug on one side (with it’s back at the fold, feet at the bottom). Shape and size of the feet are important (see images) but the rest of the bug can look however you like.
- Decorate the bug.
- Cut out bug and fold feet so they would sit flat on the water (this is important!).
- Place on the water and watch your bug walk on water!
- Make two bugs and smear some butter on the feet of one of them. The bug with buttery feet should work better.
The science bit
The molecules on the surface of the water form a thin layer, like skin. This is all thanks to a force called surface tension. The molecules on the surface are being pulled together more tightly than the molecules underneath, due to them not having water molecules above them pulling up (the molecules underneath are being pulled equally in all directions). Something that is light, like our water bugs, can balance on the surface of the water. If they break the ‘skin’ they will sink.
The bigger footed bugs will spread the bug’s weight more evenly over the ‘skin’ and therefore should be easier to balance. The bugs that have buttery feet should find it easier to walk on water as well. This is because the greasy butter repels the water. Many real bugs have oily feet to help them stay on the surface too.
(These were some of our unsuccessful bugs! I don’t think I have photographic evidence of the ones that worked but they really did!!)
Explaining it to children
Explain the water, like everything, is made up of tiny molecules (or pieces) that you cannot see. These molecules on the top of the water make a layer that the water bug is sitting on. Adaptations, such as the big or oily feet, are characteristics that bugs in real life have to help them to ‘walk on water’. Big feet make the bug more stable on the water (ask a child to balance on tip toes to see whether it is easier to balance like that or on their flat feet, which have a bigger surface area). The butter and the water don’t like to mix and so the oily feet help the bug to stay on the surface of the water.
Experiment based on an activity from the fantastic Usborne Activities: 365 Science Activities book.