Floating needle

Continuing with our surface tension bug walking on water yesterday, there are a few different things that we can do for todays experiment. You will need: a needle (or pin), a bowl filled with water (its helpful if this is see through but not essential), a tissue/kitchen towel or cotton wool pad, some washing up liquid.


Place the bowl of water so the water is not moving. Drop the needle into the bowl of water. What happens?
Take the needle out of the water, and dry it. Place it on a piece of tissue/kitchen towel or cotton wool pad. Gently place it in the water. Wait for a minute and see if the kitchen towel/tissue/cotton wool pad sinks. If it doesn't, you need to gently push it with a stick or pencil. What happens?
Note: If this has worked, the needle/pin will be floating on the water.

The needle, like the bug, is nigh enough to be supported by the skin on the top of the water, as long as it does not pierce it.

Now, pick up the washing up liquid. Place a drop into the water - what happens to the pin?
Note: the pin will sink to the bottom, because the washing up liquid breaks up the skin of the water and the needle sinks.

If you enjoyed this, you might enjoy some of our other surface tension experiments: Bug walking on water, milk marbling, repelling water. Or take a look at the 6 pages of fun activities for you to do at home and in the garden!

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