Materials Required:
- Empty box
- Scissors
- Balloon
- Rubber band
- Ammonium chloride
(available at a drug store) - Aluminium foil
- Tweezers
- Candle
Procedure:
- Cut a hole about the size of a 50-paise coin in the bottom of an empty box. (The other end is completely open.) Slice open a large balloon so that you may have a flat rubber piece. Stretch the balloon over the open end of the box and secure it with a rubber band.
- Place ¼ teaspoonful of ammonium chloride into a small cup-shaped piece of aluminium foil. Hold the aluminium foil with tweezers, while one of your parents gently heats it over a candle flame. (Ammonium chloride is a harmless chemical when it is burned.)
- Thick white smoke will begin to form. When this happens, direct the smoke into the box through the hole you have cut.
- Now, you are ready for some stunts. Tap the centre of the balloon on your box. A beautiful smoke ring will whiz out of the hole. Try to make one smoke ring pass through the centre of the other one, or try to knock down a light paper figure by shooting a smoke ring towards it!
This is what happens:
You have just produced vortex rings, which is simply whirling air. The smoke that you added serves to make the rings visible to your eyes. Do you notice that the smoke rings keep their shape for a long time? This happens because the only force that breaks them apart is the movement of air outside the rings.
