Earth science

Gilla:		Dela:

Video

Materials

• 1 heat proof container, 10 cm (4 in) in diameter
• Ethanol fuel
• 1 lazy Susan turntable
• 1 metal wire mesh trash can
• 1 trivet
• 1 pot lid on a stick (for placing on top of the container to smother the fire)
• 1 lighter with a long neck
• Lubricant
• 1 glue gun with hot glue
• 1 wood screw
• 1 drill with a drill bit for metal
• 1 screwdriver
• 1 marker pen
• Safety equipment: 1 fire extinguisher, 1 bucket of water, 1 pair of safety goggles

Explanation

You have created a fire whirl, also referred to as a fire devil. Fire whirls can occur naturally during forest fires, and they allow the fire to reach the treetops and spread there. They are formed when hot air above a fire rises and begins to rotate. When the air vortex sucks in more air from the ground, the flames also follow. Your fire whirl was created in the same way, except that you needed to assist with the rotating air. You create the rotating air using the net in the trash can. Without the trash can it will not work. The net grabs the air molecules inside the trash can and creates a spinning wind inside.

Most fire whirls are less than 1 m (3 ft) in diameter and short, but 15 m (49 ft) wide and over 100 m (328 ft) high ones have also been observed. A more extreme version of the fire whirl is the fire tornado, which originates from a thundercloud instead of from the ground. The first documented fire tornado occurred in Canberra in 2003, where a severe forest fire resulted in the formation of a thunderstorm, which in turn resulted in an approximately 500 m (1 640 ft) wide fire tornado with wind speeds around 70 m/s (157 mph). This giant fire tornado was shrouded in smoke and clouds and there are no videos or photos of it (only tracks). Instead, this photo shows a vortex in a forest fire in Oregon in July 2013.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• What happens if you remove the trash can?
• What happens if you use a smaller or larger container?
• What happens if you increase the height of the net (if you can in some way)?

Variation

You can hold a balloon above the fire, which bursts, to demonstrate that the fire rises.

Gilla:		Dela: