The Melting Phase

Posted on July 15, 2013

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A recent episode of Eureka showed a cow melting. Yeah, just melting. And a Jeep. And other stuff. It got us thinking: You know that witch at work you can’t stand? Ever catch yourself daydreaming of throwing water on her at the water cooler and watching her scream as she melts into a little puddle on the floor? Sure you did. (It’s a harmless dream, not a genuine homicidal instinct!) But can water really melt a witch?

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Not unless her biochemistry uses the water as a form of kinetic energy to break her molecular bonds. Most melting uses the kinetic energy of heat to break our molecular bonds. This is fortunate because otherwise if we washed our hands they’d simply melt away. Germs would go down the drain that way, but so does the opposable thumb and the rest of the digits. Now, if the water was hot enough then our bodies would be in trouble. But that’s unlikely. We don’t melt readily. What does, though, and what exactly does melting mean?

Melting is a change of phase/state from solid to liquid. Kinetic energy, usually in the form of heat, moves into the solid as the phase changes and causes the molecular bond to break, rearrange, and loosely re-bond molecules into a liquid state. Water is the obvious example with rigid bonds in its solid phase (ice), and loose bonds in its liquid phase. Dry ice, on the other hand is tricky. It isn’t exactly ice, and it doesn’t exactly melt. Dry ice is frozen CO2, so it is a solid form of a gas. When it changes its phase with the addition of heat, it turns back into its gas phase. This process is called “sublimation,” not “melting,” and it’s what makes the punch look extra cool at Halloween parties. Just don’t swallow any of the solid dry ice!

icemelting black.JPGGlass can be blown like bubble gum in its heated liquid state, but glass isn’t exactly solid to begin with. Glass is known as a vitreous, or amorphous solid. This means when molten, liquid glass is shaped and then cooled to room temperature, it doesn’t re-bond as strong as a solid. Instead it exists in what is called a supercooled liquid state. It has some flow at temperatures below its melting point, but not enough flow to change the shape of old windows—that’s just a myth.

The center of Earth is a molten core… somehow. How did that happen in such a cold atmosphere, anyway? We won’t go there just now, but we’ve found ways to melt minerals like iron into workable liquid form, and voila: The Bronze Age! Swords, shields, coin, guns, and cars soon followed, and had melting to thank for their existence. Better than a melting cow, definitely.

Kiped from the archives of the SyFy channel’s IdeaLab Blog for the TV show Eureka. Well kinda kiped, since I wrote it to begin with. Edited by Tiffany Lee Brown, without whom I’d be stuck in the land of curly quotes.

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Posted in: science, writing