Women's History Month Event - March 13, 2002
Women in Science sponsored a hands-on program in the University Center on March 13 in Honor of Women's History Month. WIS members assisted members of the campus community in making slime, gummy worms, Zooom Balls and liquid nitrogen ice cream. Scroll down to see the rest of the photos (just click on one for a larger version)!
	Slime Slime is a polymeric gel prepared by mixing a 4% solution of PVA, poly(vinylalcohol), with a 4% solution of sodium borate in a 2:1 ratio. Poly(vinylalcohol) is a long chain molecule called a polymer, with many hydroxyl groups, -OH, on a hydrocarbon backbone. Due to its polar structure PVA is somewhat soluble in water, though it requires heat and A LOT of stirring to get it into solution. By itself it is a viscous, colorless solution. The borate is able to hydrogen bond with the hydroxyl groups on the PVA and thereby crosslinks the chains, i.e. links chains together. Because hydrogen bonds are relatively weak interactions as compared to a covalent bond, the crosslinked material is a gel that still flows as opposed to a rigid plastic. PVA can only be purchased through a chemical supply house. However guar gum, a polysaccharide and thickening agent used in many foods, can sometimes be found in health food stores and substituted for the PVA. For more information, take an 09-xxx course!
Gummy Worms Gummy worms are made from a mucopolysaccharide called algin that is isolated from seaweed. It can be dissolved in base to form sodium alginate, which in solution it is a viscous material with a slippery, slimy feel (think about picking up seaweed at the beach!). If the sodium ion, which has a charge of +1, is replaced with a divalent cation, one with a +2 charge such as Ca2+, then more than one chain of alginate can be associated with each calcium, in essence linking the large chains together. The result is "gummy" like a gummy bear or gummy worm. The edible varieties of course contain flavorings and sugar so while ours are fun to play with, they can't be eaten!
	ZOOOM Balls These are high bouncing balls made from a patented polymeric material that swells in water. We use a purchased kit to prepare these.
Liquid Nitrogen Ice Cream Most folks know that ice cream preparation requires milk products, sugar and flavoring mixed with a healthy serving of air and frozen to the desired consistency. In many manual ice cream makers ice and rock salt were used to freeze the mixture while hand cranking adds the air. In this version the air is added in liquid form, as liquid nitrogen, and with stirring adds texture and removes heat in one easy, yet very dramatic step!

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