Curious Kids Science

Tornado in a bottle

Tornado in a bottle

Tornado in a bottle

I recently helped with the launch of a fabulous junior fiction book called “Quarks Academy” (you can read my review here). My role was to do a few science experiments that would help draw the kids in the audience at the review into the world of the young scientists in the book.

Once of the scientists, whose name is Augustine, had invented a weather machine. In keeping with her interest, I took along this tornado in a bottle experiment. In real life tornados occur because of changes in air temperature and a range of other very particular conditions but vortexes, however the occur, are fun to watch and in this experiment have interesting explanations.

In this experiment, you and your kids will create a vortex in a bottle. It is great fun, quite mesmerising and best of all, it takes hardly any time and you are likely to have what you need lying around the house and shed.

Be warned, both Lily and Ethan loved this experiment and have been arguing over whose turn it is to swish the bottle for several days now!

Materials

You will need:

  • 2 x 1.25 or 2 litre bottles – labels removed.
  • A washer that sits over the mouth of those bottles but is no larger than the bottle openings and not so small that it falls through the neck.
  • Gaff, Duct or electrical tape.
  • Food colour or a little bit of dishwashing detergent.

Optional

  • Monopoly houses
  • Glitter
  • Other small, light objects that fit into the bottle 

Method

  1. Fill one bottle ¾ full of water.
  2. Add a small squirt of detergent or a drop of food colour.
  3. Place the washer over the mouth of the bottle.
  4. Place the second bottle over the top of the first so that they are mouth to mouth.
  5. Use the tape to secure them together very firmly.
  6. Invert the bottles so that the bottle with the liquid is on the top.
  7. Observe what happens.
  8. Pick the bottles up and hold them vertically and then move them in a circular motion, as though you are stirring a pot (as quickly as you can).
  9. Place the bottles down or hold them and watch the vortex form.

The science

When you first turn the bottles over and the one with the water in top, the surface tension of the water creates a layer of water across the small hole in the centre of the washer. This prevents the water from falling through the hole.

When you rotate the bottles, the water in the upper bottle starts rotating as well. As the water rotates, the water is pulled toward the centre of the bottle. At the same time, gravity pulls the water toward the drain hole. The force breaks the surface tension. As the water drains into the lower bottle, a vortex forms. As water particles at the outside of the bottle move toward the hole, the speed of the particles increases and the force increases.

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