Given a scientific passage and an answer, generate a question for the given answer.

[Q]: Passage: When water freezes in a non-crystalline, amorphous form as frost, the water molecules are fixed in place, but not in a regular, repeating pattern. Frost and other amorphous solids are characterized by their unorganized and unpredictable structure. Because ice comes in both amorphous and crystalline forms, there are differences in the physical properties of ice such as its hardness and density. Answer: amorphous
[A]: What kind of solid is characterized by an unorganized and unpredictable structure?

[Q]: Passage: form of mechanical weathering that occurs as water expands when it freezes, wedging apart rock. Answer: mechanical weathering
[A]: What term describes weathering that occurs as water expands when it freezes, wedging apart rock?

[Q]: Passage: Helium may seem to be an exception, since it has only two valence electrons. This has to do with the fact that the n = 1 energy level has one s orbital and no p orbitals. As a result, the first energy level can be completely filled by just two electrons. It is the presence of a filled valence shell that gives noble gases their unusual stability, not anything intrinsic about the number 8. In addition to helium, the first few elements such as lithium, beryllium, and boron, have a particularly stable configuration with a pair of valence electrons rather that an octet. Answer: two
[A]:
How many valence electrons does helium have?