As I teach about water's unusual properties, we always discuss how water
expands as it freezes from 4° C to 0° C, and I have explained that the
lattice framework of ice crystals is forming. This structure has more
volume than the liquid water. I have thought that the extra volume is
taken up by empty space, but I have seen numerous references in the
textbooks which say the space is not space but is trapped air.
Am I mistaken, or is this another case of textbook error?