Chemical Concepts Demonstrated

• Chemilumininescence
• Energy released in a form other than heat, the effects of temperature on the rate of chemical reactions
• LeChatelier's Principle

Demonstration

Three lightsticks are activated by bending the plastic tube, breaking the inner vial, and shaking. Insert one lightstick into an ice water bath, another into a hot water bath, and leave the third one out in room temperature.

Observations

All of the lightsticks begin to emit a glow.  The stick in the ice water bath emits the faintest glow, but remains lit the longest.  The lightstick at room temperature is of average intensity and lasts an average amount of time.  The heated lightstick is very bright but burns out quickly.

Explanations (including important chemical equations)

The reaction releases energy in the form of light and not heat, so it is safe to pass the sticks around the classroom.  This reaction (like most other endothermic reactions) speeds up upon heating (this is an application of LeChatelier's Principle).  The reaction is so slow when cooled, in fact, that it is claimed that an activated lightstick will still emit a faint glow after six months in a home freezer.

Contributors 

• Dr. George Bodner (Perdue University)