Floating Paper Clip

Floating Paper Clip

Paper clips sink in water, right!? Using a piece of paper towel and a steady you can get them to float. Its all about the surface tension of the water. Try adding a drop of liquid detergent to upset the balance. Or floating the paper clips in different liquids. Lots of fun!

Suitable for kids aged 5+
You Need:
  • Container or bowl of water
  • Paper towel
  • Paper clips
What to do:
  1. Drop a paper clip in the water, and watch it sink to the bottom. Why does it sink?
  2. Tear off a piece of paper towel about half the size of a dollar note (size doesnt matter, as long as its bigger than the paper clip).
  3. Place the piece of paper towel gently on to the water so it floats.
  4. Carefully place a paper clip on top the piece of paper towel so it, too, floats.
  5. Wait a few seconds until the paper towel sinks. You may want to give it a helping hand by pushing down on the paper towel with a pencil or your fingers, being careful not to disturb the paper clip.
  6. Mysteriously your paper clip should now be floating on top of the water. Why did it sink before, but float now?
  7. Experiment by adding a drop of liquid detergent to the water. How does it affect the floating paper clip? Why? Can you get the paper clip to float in different liquids? Why?
Photo Credit: AyeKay

Why is it so?

Paper clips sink in water because they are heavier, or more dense than water. Gravity pulls harder on denser objects. The water pushes back up on the paper clip, against gravity, but not with enough force to keep the paper clip afloat.

So how is it possible for the paper clip to float!? With a little thing scientists call surface tension. The surface of water has what is known as surface tension, a bit like a skin. The particles or molecules that make up water are attracted to each other in all directions and, just like good friends, stick tight together. The paper towel helps you lower the paper clips onto the surface of the water without breaking the skin. So the paper clip is not truly floating, it is being held up with the surface tension of the water. Lots of insects, like water striders, use this skin to walk across lakes and streams.