It is fairly uncommon for liquids to expand when they fuse. I think bismuth does the same thing, and water does, as you mentioned, but don't know of anything else offhand. In the case of water it has to do with a crystal structure that requires more space than the amorphous liquid does*. I don't know what the mechanism is with gallium. It has conchoidal fracture, which is commonly seen in amorphous glassy solids, so I think it may be some other mechanism, but it may just be a very fine grained crystalline structure.<br>
<br>-N<br><br>*Water molecules are approximately L-shaped. When they can flow feely around each other they can spoon and hook around each other in all sorts of ways that increase the density. When they are frozen into a regular grid, the inside of the L is empty, so they are packed less densely. Pressure on ice near the melting point can disrupt the crystal structure and re-liquify it, which is one of the reasons ice skates work so well. A gallium skating pond might work too, though gallium loves alloying so much it might just dissolve the blades (it dissolves aluminum readily, don't bring it on a plane!) , and in its liquid form it's kind of sticky.<br>
<br><br><div class="gmail_quote">On Fri, Jun 5, 2009 at 3:48 PM, d p chang <span dir="ltr"><<a href="mailto:pchang@macrovision.com">pchang@macrovision.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Noah Balmer <<a href="mailto:noahbalmer@gmail.com">noahbalmer@gmail.com</a>> writes:<br>
<br>
> I'm surprised to see it stored in a glass vial in that image<br>
<div class="im">> though, because it expands by a few percent when it solidifies, and<br>
> will often break rigid containers.<br>
<br>
</div>wow. i thought water was 'weird' that it expanded when it became a<br>
solid. am i just mis-remembering something or is this actually common?<br>
<br>
\p<br>
---<br>
I know that you believe that you understood what you think I said, but I<br>
am not sure you realize that what you heard is not what I meant.<br>
- Robert McCloskey<br>
</blockquote></div><br>