Walking on Water – Potty Science Club

21/04/202109:0021/04/2021 09:16Leave a Comment

Hello and welcome to The Potty Science Club. Here we’ll be experimenting using equipment and items you can find in your own home. All our experiments will be safe and simple and reflect an item or exhibit held in the Museum’s collections. So follow along with us and give it a go to become a Potty Scientist.

Today’s experiment looks at the question:

‘Why can some insects such as Mosquitoes and Pondskaters actually walk and live on the surface of water?’

What is it that enables these insects to do this? There’s a combination of factors –

  • The insect’s minuscule weight
  • water repellent hairs on their feet
  • the structure of their feet  
  • plus the surface tension of the water

These all combine to allow insects like pondskaters to walk on water. Today’s experiment will look at one of these factors – surface tension. To demonstrate this at home you will need the following items:

  • A pencil
  • A paperclip
  • A small piece of kitchen tissue roll
  • A plastic tub or container to hold water
  • A towel

First, carefully pour some water into your container and let it settle for a moment. Now pick up the paperclip and try to float it on the surface of the water.

It sinks of course. This is because the paperclip breaks the surface tension of the water,

Let’s try again!

This time carefully float the piece of kitchen tissue on the water and then gently place the paperclip onto the middle of the floating paper. You then be able to use the pencil to push the paper down away from the paperclip. If you do this properly the paperclip will float on the surface of the water. This is because the paperclip did not break the surface tension of the water this time.

I have made a short video of my attempt so you can see how it works!

So how does surface tension work? Water molecules are more attracted to each other than to other materials creating a force to hold them together. This what we call surface tension.

Surface tension can also be seen if you overfill a glass – can you see the surface of the water bulging slightly above the top of the glass? This bulge of water is held in place by surface tension.

So have a go at floating a paperclip yourself and be amazed at the magic of nature.

Hope you’ve had a Potty time – subscribe to our YouTube channel, follow us on Facebook and keep an eye on our website blog for future episodes and join us next time for another experiment.

By Rob Gagliano, Casual Learning Development Leader and Natural Science Collections Volunteer

Written by museumvolunteers - Modified by Glenn Roadley (Curator, Natural Sciences)

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