In the afternoon of May 20th, three McMurry science faculty (Wayne Keith, Pam Veltkamp, Ed Donnay) performed a series of science demonstrations for both classes of the McMurry Center for Innovation fifth grade students. The outdoor classroom north of the greenhouse was used both because of potential fumes created by the demonstrations, and so that all students could attend together.
The program began with placing a banana and a racquet ball into a dewar of liquid nitrogen. While those were cooling, several flowers were frozen and shattered on the tables. Two balloons were alternately contracted and expanded by placing them into and taking them out of the liquid nitrogen. Once the ball was frozen, it was shattered onto the pavement, making a loud pop as it was broken. The banana was then used to hammer a nail into a board, which was less than successful as the banana kept breaking apart. The nitrogen was then transferred into a shallow “dog dish” dewar and used to freeze some oyster crackers. Each student and teacher had a chance to eat a frozen cracker, resulting in “smoke” issuing from their mouth or nose. The remaining LN2 was then poured out onto the ground, making a big cloud to the amusement of the students.
The next demonstration was making “elephant toothpaste” by mixing dish soap, hydrogen peroxide and yeast. After that was a demonstration of a “fire snake” growing out of a beaker with a mixture of powdered sugar and hydrochloric acid.
The final demonstration was of a thermite reaction (powdered aluminum and iron oxide) creating molten iron that burned through a Coke can into a container of sand. It was a fun day for all involved, and the best way possible to dispose of a bit of leftover liquid nitrogen.
Story provided by Dr. Wayne Keith