One evening long ago, when I was about fourteen of fifteen years of age, I was scanning a detailed copy of the periodic table of elements for elements with interesting properties. The melting point of gallium caught my eye — 29.76 °C. Hmmm. Wasn’t room temperature around 20 °C and body temperature 37 °C? Wouldn’t that imply that gallium, like chocolate, would melt in your hand (despite having all the appearances of being a normal solid chunk of metal)? Is that even possible? It seemed so strange for a metal to be able to do that.
But where would I get some? The scientific supply houses of the day didn’t sell to individuals (even if I had the money for a rare and esoteric reagent like elemental gallium). I’d just have to be satisfied with imagining having some and what it would be like.
Enter the Internet, where every market (no matter how small) seems to have a vendor willing to satisfy it. There’s now several places on-line that cater to the whims of those looking to collect a few oddball elements. So I paid the price and ordered some.
It’s even more mind-blowing than I imagined it to be. Chocolate, containing a mixture of fats, is somewhat soft at room temperature and becomes even softer before it melts. When it melts, it’s thick and viscous. Not so with gallium. It’s a metal, about as dense as iron. It’s shiny shivery-gray, like most metals. At room temperature, it’s hard, like most metals. It rings when you drop a small chunk on a hard surface, just like most other metals.
When I hold the plastic bag containing it (it’s very sticky and messy when molten, stains skin, and its toxicity is poorly-researched), at first nothing happens. Like all metals, it’s a good conductor of heat so the bag feels cool to the touch. Eventually, it feels slippery inside, as if it’s melting.
It is melting, of course, but my mind tells me it can’t be. Metals just don’t do that. With one exception, mercury, every metal I’ve personally experienced up to this point is solid at room temperature. And mercury is liquid to well below the freezing point of water. Touch a melting metal and you’ll either get frostbite or a nasty burn. Decades of experience say metals simply do not undergo liquid/solid transitions anywhere close to room temperature.
Yet, there it is, acting contrary to experience (and in accordance with what that old, long-gone, periodic table said). And when it melts, it’s fluid, not a thick viscous soup. It’s obviously not mercury (it’s brighter than mercury), but was it really a solid heavy chunk that rang when dropped on the table a few minutes ago? Objectively, I know it’s so, but my mind keeps telling me it can’t be: I must be imagining that recent memory; it’s just to fluid, too thoroughly a liquid, for that to have been the case.
Because it’s sticky, it makes a mess inside the bag. After it solidifies, there’s lots of little flakes inside in addition to the now-solid chunk. No problem — I just weld the flakes back onto the big chunk, using my finger as a soldering iron. Even though I know that idea should work, and I’ve now experienced melting gallium first-hand not too long ago, I’m still surprised when it does.
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