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Activity

Luminescent candy

Summary: 
Smash wintergreen lifesavers to show luminescence from mechanical cleavage (Triboluminescence). Same mechanism as lightening.
Science content (2016 curriculum): 
Chemistry: Atoms, Molecules (3-7)
Chemistry: Chemical Changes (2, 7)
Physics: Light and Sound (1)
Physics: Energy forms, Conservation of Energy (1, 3, 4, 5)
Science topic (2005 curriculum connection): 
Physical Science: Light and Sound (grade 4)
Physical Science: Chemistry (grade 7)
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Lessons activity is in: 
Materials: 
  • dark room e.g. behind curtains on the school stage
  • wintergreen lifesavers (must contain methyl salicylate)
  • hammer
  • dark cloth
  • clear piece of plexi, or other hard plastic
  • tray to contain flying lifesaver pieces
Procedure: 

This activity needs quite a dark area, so give students a while to get their eyes adjusted to the dark first.

Place a wintergreen lifesaver on the cloth under the piece of plexi.
Smash the plexi with a hammer.
As the candy gets broken into small pieces, flashes of blue light are seen in different places under the plexi.

Young student explanation: when you hit the candy you put in energy. The energy comes out again as light. It is lightening on a very small scale.

Older student explanation: As you hit the candy you separate charged particles. As electricity flows between them it excites the nitrogen in the air. The excited nitrogen re-emits the energy as light - mostly UV but some blue. This happens with regular sugar, but the light emitted is mostly UV so not so visible. This is the same chemistry as lightening. The wintergreen flavour amplifies the light - methyl salicylate is a fluorescent molecule: it absorbs the UV emitted by the nitrogen and re-emits blue light, so making the light given off more in the visible range where we can see it.

Grades tested: 
Gr 1
Gr 2
Gr 3
Gr 4
Teacher: 
Ingrid
Teaching site: 
Bayview Elementary Science Club
General Gordon Elementary Science Club
Activity originally developed and delivered: 

Gordon Elementary science Club