Floating Toothpick Trick

Floating Toothpick Trick

If you try this toothpick trick, be ready to do it over and over again. It’s just so fun to watch! First, you float toothpicks on the surface of the water. Then, just a touch of dish soap makes the toothpick shape fly outward.

This toothpick experiment is a really fun way to explore surface tension with kids. Just floating the toothpicks on the water is quite a discovery.

What’s going on?

Water molecules tend to want to hold onto each other. Think about how water joins together to form little beads when you drip it onto a smooth surface like a plate or wax paper. This is called surface tension.  The water molecules in your dish are holding onto each other so tightly that the toothpicks are able to float on top.

Adding dish soap breaks apart the bonds that hold the water molecules together. This disturbs the floating toothpicks and pushes them outwards, which breaks up the square. That’s how the toothpick trick works!

3 - 16
Est. Time:
<30 mins

How we did it:

Materials List

  1. toothpicks
  2. bowl
  3. dish soap
  4. water
  1. Gather the materials you need to perform the toothpick trick. 

  2. Fill the dish with water and wait for minute until the water is completely still. This is important because placing the toothpicks is a pretty delicate operation.

    Next, very gently place four toothpicks on the water so they form a square. Overlap the ends of the toothpicks just a bit. This will help them hold their square shape. This can take a little bit of practice to get right. If one of the toothpicks sinks instead of floats, take it out and get a fresh one.

  3. When you have a floating square, touch another toothpick in the middle of the square. Nothing happens, right?

    Now dip  another toothpick into the dish soap. Touch the soapy toothpick in the center of the square. Watch the toothpicks fly apart! My 7-year-old thought this was hysterically funny and insisted that I do it again (and again).

  4. We found that we could usually make the toothpicks move once more by dipping into more dish soap, but that’s it. After the toothpicks won’t move any more, you’ll need to dump out the water and start fresh if you want to try again. (When you float the toothpicks, the water can’t have soap in it.) We also had fun trying out different shapes for our moving toothpicks. I liked the zig-zag, which was fun to watch and also easier to build than a square. For a challenge, try a 5-sided figure.