Kinetics of Light Sticks

Materials

2-4 10 cm Light Sticks

3 Beakers:  1 with Ice Water, and 1 with Hot Water (~50 C)

Gloves and Goggles

Procedure

Cyalume light sticks demonstrate how temperature affects reaction rate. Put one light stick in hot water and one in ice water. Dim the lights and compare the luminescence with the room temperature lightstick. One can compare length of luminescence based on temperature, the stick in hot water fading first. The temperature must not go above 70^o or the plastic tube will melt.

Using a light meter in a darkened room, the activation energy can be measured by plotting ln(light intensity) vs. 1/T, T = temperature. The activation energy is approximately 56.4kJ/mole.

Once put in hot water, the light stick lasts only about 5 minutes.

Waste Management

If unbroken, the light Sticks can go in the trash.  If broken, place in plastic bags and give to EH&S.