I2-42
Demonstrate how a flame burns in the absence of normal convection.
A candle, attached to the lid of a one-gallon jug, is lit and the lid screwed onto the upside-down jug. Throw the upside-down jug into the air and catch it or hold the upside-down jug high and drop it and catch it as it falls. While it is falling, the system inside the jar is in a weightless environment, so convection currents cease. In normal burning, the hot air rises by convection, allowing cooler air containing more oxygen to continuously feed the fire. Without these convection currents the candle should immediately go out, BUT IT DOES NOT.
I2

A candle mounted on the lid of a gallon jug is lit, and the lid quickly affixed to the jug. In this configuration the candle will remain lit for over one minute before the oxygen in the jug is sufficiently used up by the combustion process and the flame is extinguished.

Now suppose that the candle flame is lit and the lid again quickly affixed to the jug. However, the bottle is now dropped about six feet starting from the orientation shown in the photograph below.

i2 42

What will happen? In particular, by the time the jug falls six feet the candle flame will:

  • (a) burn more brightly.(b) remain at about the same brightness.
  • (c) burn less brightly.
  • (d) go out.