science tuesday :: water surface tension

Still working from this book, today we decided to look at surface tension.

We made floating beasties and soap powered fish.

Floating Water Beasties
We made our cardboard little monsters (we actually made a whole load of them but felt that only three could fit in the tray at any time.)

Then we carefully bent their feet out and placed them in the tray of water. Before we put them in we placed bets on whether we thought they would sink or float.

After we'd seen the amazing floating beasts, I asked them why they thought they floated. There was a variety of suggestions, "magic" always featuring.

I read out from the book about the surface of water having a very thin skin and that by having big feet the weight of the beasties is spread out over the skin. Of course, then beasties with teeny feet were made and guess what....they sank!

Theory proved :)

Soap powered fish

We made fish from card, decorated them (very important) and then applied the tiniest bit of washing up liquid to the point in the fishy tail. Then we carefully set them on top of the water, and watched them go! This would be fun to do in the paddling pool in Summer, so I need to make a mental note to remember to do this.

This little experiment nicely demonstrates the surface tension of water interacting with another element - in this case the detergent. when the soap touches the water it creates a soapy film behind the fish that pushes the water skin away.

The best bit....combining craft with science. This is (for us) such a good way of getting every one involved.