I'm sure this is for most of you a basic question, but it really puzzles me:

How it is that, even though all materials expand as they get warmer, and contract (maybe these are not the correct terms) when get colder, water exapands when freezes.

Thanks a lot.

  • 2
    $\begingroup$ First, the thermal expansion coefficient for a given material is not a constant - it varies with temperature and can be both positive and negative depending on the temperature. Second, to add to the answer below, there are at least 4 elements that exhibit a solid phase at lower density than the liquid, namely silicon, germanium, antimony, and bismuth. Both silicon and germanium have the fairly open diamond lattice in the solid, yet are 8-12 fold coordinated metallic liquids. $\endgroup$ – Jon Custer May 13 '15 at 13:24
  • $\begingroup$ Marked as duplicate but t just says there is a different lattice structure. No explanation as to why a different lattice structure forms with lowering of temperature. Is that just assumed knowledge, or something we just should accept ? $\endgroup$ – phil soady May 1 '18 at 1:20

The expansion upon freezing comes from the fact that water crystallizes into an open hexagonal form. This hexagonal lattice contains more space than the liquid state.

| cite | improve this answer | |
  • $\begingroup$ And how do other materials freeze, or solidify? $\endgroup$ – Masclins May 13 '15 at 11:55
  • $\begingroup$ how does that explain the change of lattice structure ? $\endgroup$ – phil soady May 1 '18 at 1:11

Not the answer you're looking for? Browse other questions tagged or ask your own question.