Vikram Singh, 8R Crystals and Triboluminescence In our Chemistry lessons on saturated solutions and solubility curves we learnt that a saturated solution is a solution in which no more solute can dissolve in the solvent at that temperature. In general, the hotter the solvent, the more solute (solid) it can dissolve i.e. solubility increases with temperature. So if a saturated solution at high temperature is allowed to cool down its solubility decreases i.e. less solute can dissolve in the solvent and so some of the solute should come out of solution and crystallise. To demonstrate this we had grown some sugar crystals. For this we had prepared a saturated solution of sugar (the solute) with boiling water (the solvent) and let the solution cool. We suspended a star made of pipe cleaner in the hot saturated sugar solution and set it aside to cool. After a few days, we removed the star and it was covered with sugar crystals. Since the star was added to a saturated sugar solution at nearly the boiling temperature of water, as it cooled, the solubility of the water decreased. So the water could not hold as much sugar in solution and so some sugar came out of solution and crystallised onto the star. While waiting for the crystals to form, I did some research on how crystals are formed and what interesting properties they have. One very intriguing phenomenon I came across was Triboluminescence (described below). I wanted to observe it myself so I grew more crystals and added food colours to have different colour crystals. Triboluminescence is when a flash of light is produced when a material is crushed, ripped, scratched, or rubbed. The term triboluminescence comes from the Greek word tribein (to rub) and the Latin word lumen (light). Triboluminescence can be observed as flashes of light when sugar crystals are crushed in a dark room. Triboluminescence is also called fractoluminescence meaning light emitted when crystals are fractured. How to observe triboluminescence? Apparatus: Sugar Crystals, pliers, and a dark room preferably at night, a large clear plastic container(optional) to contain the flying pieces of crushed sugar Method: • Go to a dark room and let your eyes adjust to the darkness. • Place a sugar crystal between the prongs of the pliers and place it inside the clear plastic container. • Crush the crystal. Page 1
Transcript
Vikram Singh, 8R
Crystals and TriboluminescenceIn our Chemistry lessons on saturated solutions and solubility
curves we learnt that a saturated solution is a solution in which no more solute can dissolve in the solvent at that temperature. In general, the hotter the solvent, the more solute (solid) it can dissolve i.e. solubility increases with temperature. So if a saturated solution at high temperature is allowed to cool down its solubility decreases i.e. less solute can dissolve in the solvent and so some of the solute should come out of solution and crystallise.
To demonstrate this we had grown some sugar crystals. For this we had prepared a saturated solution of sugar (the solute) with boiling water (the solvent) and let the solution cool. We suspended a star made of pipe cleaner in the hot saturated sugar solution and set it aside to cool. After a few days, we removed the star and it was covered with sugar crystals.
Since the star was added to a saturated sugar solution at nearly the boiling temperature of water, as it cooled, the solubility of the water decreased. So the water could not hold as much sugar in solution and so some sugar came out of solution and crystallised onto the star.
While waiting for the crystals to form, I did some research on how crystals are formed and what interesting properties they have. One very intriguing phenomenon I came across was Triboluminescence (described below). I wanted to observe it myself so I grew more crystals and added food colours to have different colour crystals.
Triboluminescence is when a flash of light is produced when a material is crushed, ripped, scratched, or rubbed. The term triboluminescence comes from the Greek word tribein (to rub) and the Latin word lumen (light). Triboluminescence can be observed as flashes of light when sugar crystals are crushed in a dark room. Triboluminescence is also called fractoluminescence meaning light emitted when crystals are fractured.
How to observe triboluminescence?
Apparatus: Sugar Crystals, pliers, and a dark room preferably at night, a large clear plastic container(optional) to contain the flying pieces of crushed sugar
Method:
• Go to a dark room and let your eyes adjust to the darkness.• Place a sugar crystal between the prongs of the pliers and place it inside the clear plastic
container.• Crush the crystal.
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Vikram Singh, 8R
Observation: You should be able to observe some flashes of light as the crystal smashes.
Although I observed the flashes of light (triboluminescence) with all the different crystals, the flash was so quick that I could not take any pictures of it. The picture above is from the BBC - Bang goes the theory website (http://www.bbc.co.uk/bang/handson/sugar_glow.shtml).
Why does triboluminescence happen?
The phenomenon of triboluminescence is not fully understood. Scientists believe that when you apply enough mechanical pressure to break a crystal, some of the atoms along the fracture lines are ripped apart, separating some of the electrons from their nuclei. When enough charge has accumulated, the electrons jump back across the fractures. They collide with molecules in the air, ionising nitrogen gas molecules and making them glow with a blue luminescence.
Scientists have compared the spectrum of light emitted during the triboluminescence of sugar and found it to be the same as the spectrum produced by lightning which is caused by electrical charge passing through the air, exciting the nitrogen gas molecules in the air. So triboluminescence can be thought of as lightning on a very small scale. The light produced by triboluminescence is very faint because most of the light emitted is in the ultraviolet spectrum (wavelengths < 380nm), and only a small fraction is in the visible spectrum.
Triboluminescence has been observed in many minerals like quartz, fluorite, calcite, many feldspar minerals and many other materials.
The first known use of triboluminescence was by the Uncompahgre Ute Indians form central Colorado. They built ceremonial rattles from buffalo hide and filled them with clear quartz crystals from the mountains of Colorado. When the rattles were shaken at night, the quartz crystals rubbed against each other and produced flashes of light, visible through the translucent buffalo hide.
References: 1. Wikipedia: Triboluminescence. http://en.wikipedia.org/wiki/Triboluminescence2. http://geology.com/minerals/triboluminescence/3. Wintergreen Candy and Other Triboluminescent Materials: Linda M. Sweeting, Department of Chemistry,
Towson University, Scientific Experiments at Home website series, September, 1998. http://pages.towson.edu/ladon/wg/candywww.htm
4. Cape Cod's "Magic" Quartz Pebbles: Robert N. Oldale, United States Geological Survey, Coastal and Marine Geology Program, website article, May 2007. http://woodshole.er.usgs.gov/staffpages/boldale/pebbles/
