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Liquid Nitrogen boils at -200 degrees Celsius (-328 degrees Fahrenheit) and allows scientists to observe low temperature processes. In the photos below, the effects of such low temperatures are dramatically evident as balloons, shrink to practically no volume when the gas molecules trapped inside lose kinetic energy and take up much less space. A rose, exposed to such low temperatures, shatters when struck against a table as the petals have no elasticity. Marshmallows turn into cool, crunchy treats for all to enjoy. Liquid nitrogen is primarily used in industry where low temperatures are needed as in infrared cameras. Thanks to Carol Johnson and the Physics Learning Center at UC Santa Barbara for loaning the dewars which made this possible!
Notice the volume of the balloons as they are just taken from the liquid nitrogen.
This blue balloon has a temperature close to -200 degrees Celsius but is able to be held because it is a poor thermal conductor and draws little energy away from my hand.
Notice the size of the balloon after only 5 seconds exposure to 20 degree Celsius room air. The gas molecules inside the balloon have regained their kinetic energy and now vibrate much more causing their total volume to increase and expanding the balloon.
This piece of rubber from a mousepad shatters when it hits the ground (picture unavailable) because at such low temperatures the rubber loses its elasticity and becomes brittle.
This small beaker contains liquid nitrogen, which is visibly boiling. Liquid nitrogen poses little danger in small quantities because it evaporates almost on contact with high temperature objects such as our skin. Large quantities, however, can cause frostbite, and even result in the death of tissue and eventual amputation.
Here a white rose is shown just after being taken from the liquid nitrogen.
The dramatic effects of low temperatures are clearly visible to students as the flower shatters to hundreds of pieces in front of them. |
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