From: Monte Davis 

"John Beamish"  wrote:

>IIRC from my grade 10 physics/chem class:  change of state of matter from
>gas-to-liquid or liquid-to-solid or the return route involves substantial
>energy transfer.  Once the change of state occurs, the energy involved in
>further transitions within the state is demonstrably less.

Water: takes 1 calorie/gram (by definition) to warm it by 1 degree C (or
K); it gives off the same when it cools by 1 degree. But at
freezing/melting, there's an *80* cal/g "ledge" of latent heat;
at boiling/condensation, a *540* cal/g "ledge." All the numbers
are lower for most other substances, but the ledges are still there.

So misting water in a citrus orchard or on a strawberry field can save the
fruit on a freezing night, releasing heat as it freezes. So live steam
produces  terrible burns, depositing heat as it condenses. Most of all, the
high latent heats of water moderate the earth's temperature. The big energy
demands at 0 C and 100C act as flywheels. Or governors, or sheet anchors,
or whatever metaphor you like for "smoothing out extreme
variation."

Monte Davis
http://montedavis.livejournal.com

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