Take Home Bonus Lab

Take Home Lab BONUS: Mechanoluminescence:

Making Things Light Up

Question: Why does a Life Saver light up when crushed?

Safety: Be sure to look around before turning the lights off to notice any hazards. Be very careful biting down hard on candy, especially if you have had dental work done.

Materials: several Wint-O-Green Life Savers, transparent tape, sugar cube, plastic knife

Procedure: Mechanoluminescence basically means making something light up with the use of force to create a chemical reaction. There are many substances around you that are mechanoluminescent (also called triboluminescent or fractoluminescent). You will experience three substances to see how they light up.

            Wintergreen (methyl salicylate) cannot luminesce (give off light) through a force, but it can luminesce when ultraviolet light shines on it. The combination of the sugar and the wintergreen creates this effect. The sugar gives off some ultraviolet light when it is crushed, and the wintergreen absorbs the light and gives it off again in a color that our eyes can see. The energy the sugar gives off is mostly at about 350 nanometers (nm). Our eyes cannot see that light the same way our ears cannot hear a dog whistle. The wintergreen absorbs that energy and re-emits it at about 450 nm, which we can see.

1. Have the two Wint-O-Green Life Savers with you and the transparent tape roll ready so that you can find the end in the dark.

2. Go to a room with no windows. A bathroom works best. It must get very dark in this room and there must be a mirror. Let your eyes adjust to the darkness for 3-5 minutes.          

3. Put the Life Saver standing up between your upper and lower teeth. Look into the mirror and bite down hard with your lips open. Keep chewing and record what you see. Repeat with the second candy.

4. Grab the end of a transparent tape and quickly pull about 12 inches (30 cm) off the roll. Record your observations.

5. Take your sugar cube and scrape it quickly with a plastic knife and observe. Record your observations.

Data:

Substance:	Color observed:	Wavelength (in nm):
Life Saver
Sugar cube
Transparent tape

Post-Lab Questions:

1  Copy the data table for all three trials.

2. What color did you see the candy luminesce?

3. What color did you see the transparent tape luminesce?

4. What color did the sugar cube luminesce?

5. Find a picture of the electromagnetic spectrum online (search Wikipedia for visible spectrum article) and answer the following questions:

   a. What color should 450 nm be? Did that match your answer to #1?

   b. What do you think is the wavelength of the light given off by the transparent tape? Do you think that sugar or wintergreen had anything to do with this?

    c. What do you think is the wavelength of the light from the sugar cube?