Jack L. Lambert and Larry M. Seitz Kansas State University Manhattan
A Model of the ice Structure
ing a thin, continuous layer of the emery particles. The reaming tool is best used in a lathe. The cork balls were reamed out until the total outside-to-outside distance of the cork ball plus table tennis ball was 12s/32 in., measured with calipers. The 105' bond angle can be estimated with sufficient accuracy after the angle in the first molecule is measured carefully. Cementing one water molecule to the next requires that each be propped in proper juxtaposition or held by hand until the cement hardens. Attention must be given to the random directions of the hydrogen bonds as they should not tend to point all in the same direction.
The ice model shown in Figure 1 has proved useful as an instructional aid. It is light, strong, and as nearly representational as a simple physical model can be (see Pauling'). The individual water inolecules are constructed of ll/rin. diameter table tennis balls and 1 - i n . diameter conlposition cork balls.* Good quality nlolded expanded polystyrene balls3 having a snlooth surface should serve as well as the more expensive table tennis balls.
Figure l a .
Ice model, front view.
Figure 1 b.
Ice model, top view.
The cork balls were cut, drilled, and reamed as sholvn in Figure 2 and ceinented to the table tennis balls a t the proper angle with a fast-drying Duco cement. A drill of a t least 3/i-iu. diameter held in the chuck of a lathe was used to bore holes in the cork balls as shown. A reaming tool was made by cementing a table tennis ball to a short piece of large diameter wooden dowel rod, the end of which was shaped to the contour of the ball. A grinding surface of coarse einery particles was prepared by spreading a thin coat of glue on the ball and apply-
Figure 2 ,
The scale is slightly less than 1.5 cm = 1 -1. The 0-0 internuclear distance in ice is 2.76 .iof , which the 0-H distance is 0.96 A. When the covalent radius of H (0.28 A) and the van der Waals radius of oxygen (1.4 A) is added to the 0-H distance, 2.64 A of the 2.76 A can be accounted for. The oxygen atoms in the model are thus slightly oversize relative to the other distances to permit contact with neighboring molecules. Probably a greater distance than the covalent radius should be allotted to the hydrogen atoms in the direction of their hydrogen bonds to the oxygen atoms of neighboring water molecules, but oversize hydrogens would be more noticeable than oversize oxygen atoins in the individual water molecules.
The construction of this model was a portion of the research for which Mr. Seitz received support in the form of a stipend from an NSF Undergraduate Research Participation Program at Kanam State University. L P ~ ~L., ~"The ~ Nature ~ a ,of the Chemical Bond," 3rd ed., Cornell Univ. Press, Ithasa, N. Y., 1960, pp. 464-9. a See Lamhert, J. L., J. Chem. Educ., 41, 41 (1964) for the names of commercial suppliers. The composition cork halls cost 51.45 per dozen or $14.40 per grass. The Plasteel Corp., 26970 Princeton, Inkster, Mich., s u p plies 1.5-in. diameter balls s t $1.90 per hundred.
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Journal o f Chemicol Education
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