Kitchen Science Experiments

Strange Glows from Sugar

Sun, 25th Feb 2007

Part of the show Parasites and Clean Water

What you Need

Lumpy Sugar

Some Lumpy Sugar, or sugar lumps.

Pliers

A Pair of Pliers


Dark room

A very very dark room

What to do

Crushing SugarGet the Pliers and a lump of sugar somewhere you can find them in the dark.

Turn off the lights and wait for at least 2 minutes - this will make your eyes much more sensitive.

Carefully crush a lump of sugar in your pliers. - watch the sugar and see what happens.

What may happen

With any luck you should see little flashes of blue-green light as you crush the sugar.

Why does it happen?

When you crush the lump of sugar, you are fracturing sugar crystals, sugar crystals are slightly asymetric and, when you apply pressure, on a molecular scale some areas are slightly positive and some slightly negative.

Sugar Crystal

if the crystal breaks it will sometimes have more positive charge on one side of the fracture and more negative on the other.

Cracked sugar crystal

 

 If the two halves of the crystal are pulled apart you are seperating the positive and negative charges which takes quite a lot of energy (a bit like pulling two magnets apart). Voltage is a measure of how much energy each charge has got so the voltage builds up.

Crystal Sparking

At some point this voltage gets large enough for the charge to flow through the air as a spark. In order to do this it has to rip air molecules apart, giving them lots of energy. They release some of this as light which creates the strange glows.

This effect is called triboluminescence, and similar effects can be seen in lots of different materials, from sellotape to flint pebbles on the beach

Dave Ansell

Multimedia

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