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Re: Regarding "frost warning" help

Square Foot Gardening List - http://www.flinet.com/~gallus/sqft.html

On Wed, 16 Jun 1999 21:26:08 -0500, "Autumn Donaldson"
<autumn@up.net> , late of Pablo Fanques Fair wrote:

>Square Foot Gardening List - http://www.flinet.com/~gallus/sqft.html
>
>I might be ignorant, but something from my Grade 9 science class is nagging
>at the back of my mind about how when a substance changes phases (is that
>the right word? ) from gas to liquid or liquid to solid, and vice versa,
>energy is given off.  So, my guess is that by thawing the ice by spraying it
>with water, energy is given off, thereby warming the plants and protecting
>them from damage.  Farmers do it all the time in Florida with their citrus
>crops.

You are half-right. When a gas condenses, or a liquid solidifies,
energy is given off. But when the opposite happens, energy is
absorbed. This is why air conditioners work. A liquid is condensed,
and cooled by air flowing over the coil to remove as much energy as
possible. Then it is allowed to very quickly turn into a gas, and in
so doing absorbs a tremendous amount of heat energy from the
surrounding air. This cools the air.


-- 
Kevin B. O'Brien                  TANSTAAFL
kob1@ix.netcom.com
"It does not matter how slowly you go so long as you do not stop."
                            Confucius

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