Sophie Duncan charms a snake with hot air

4th June 2004 at 01:00
These investigations explore the behaviour of hot air and hot water.

Take a small bottle and a large clear bowl or tank. Fill the tank three quarters full with cold water. Fill the small bottle with hot water, and add a couple of drops of food colouring. Put a top on the bottle, and make a small hole in the top. Lower the bottle into the tank with your finger over the hole to stop any water escaping.

Settle the bottle on the bottom of the tank with the top submerged and remove your finger.

Observe what happens. The hot water will rise through the hole. As it is coloured you can observe it moving to the top of the tank.

Repeat the experiment using cold water in the bottle and warm water in the tank.

What happens if you carefully pour the cold coloured water into the bottom of the tank?

Finally, make a hot air detector. Take a piece of A4 paper and cut out a circle with a diameter that is as wide as the paper's width.

Starting from the middle of this paper disc, mark out a spiral snake, making sure that the body is at least 1cm wide. Cut out the spiral, and decorate.

Attach a thread to the inside end of the snake and suspend it above a table lamp, making sure it is not in a draught and will not touch the light bulb.

Turn the lamp on and watch what happens. The snake should spiral round as the air, heated by the bulb, rises.

Take two similar table lamps and put an energy-efficient light bulb into one and a normal light bulb into the other. Suspend a "snake" above each lamp, and turn them on.

Less heat will be given out by the energy-efficient bulb, and the snake above it will not move as much as the one above the normal bulb.

Log-in as an existing print or digital subscriber

Forgotten your subscriber ID?


To access this content and the full TES archive, subscribe now.

View subscriber offers


Get TES online and delivered to your door – for less than the price of a coffee

Save 33% off the cover price with this great subscription offer. Every copy delivered to your door by first-class post, plus full access to TES online and the TES app for just £1.90 per week.
Subscribers also enjoy a range of fantastic offers and benefits worth over £270:

  • Discounts off TES Institute courses
  • Access over 200,000 articles in the TES online archive
  • Free Tastecard membership worth £79.99
  • Discounts with Zipcar,, Virgin Wines and other partners
Order your low-cost subscription today