In a common example of supercooling, putting a bottle in a freezer and then agitating it nucleates the formation of this substance. For 10 points each:
[10e] Name this solid substance that unusually has a higher volume and lower density than its liquid counterpart due to increasing rigidity between its O–H hydrogen bonds.
ANSWER: ice [or water ice; prompt on H2O (“H-2-O”); reject “water”]
[10m] Most instances of ice crystals on Earth exist in the Ih (“eye-H”) form, whose symmetry aligns with this shape. Face-centered cubic lattices and a lattice named for this shape are the only two lattices that are close-packed.
ANSWER: hexagons [accept hexagonal symmetry; accept hexagonal close-packed]
[10h] The space group for hexagonal ice contains one of these symmetry operations consisting of a reflection and parallel translation. Hermann–Mauguin (“mo-GAN”) notation uses a lowercase a, b, or c to represent this symmetry operation.
ANSWER: glide plane [or glide plane symmetry; prompt on transflection]
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