h a l f b a k e r yLike gliding backwards through porridge.
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Several chambers in a large clear thermometer are filled
with
substances arranged by a gradated
freezing/melting/boiling
point. This might be stuck outside your window.
Each chamber would either be filled with ice, liquid or
gas
depending on the temperature.
To see what the temperature
is you'd look at the
chamber
that was in transition, so for instance, if it were 70
degrees,
you'd look at the chamber marked accordingly and see
that
the liquid has turned to gas. All the chambers to the
right
of
it are still liquid, all to the left are gas or some liquid
gas
combination. You'd look at the one that was all gas or all
ice to see what the temp was.
On a cold day the chamber marked 32 degrees would
transition from liquid to ice.
Pressures and chemical makeup of the substances would
determine at what temperature they transitioned from
one
state to the other.
The 32 degree chamber would be just water, then you'd
do
whatever you needed to the other chambers to make
them
react the way you wanted at the appropriate
temperature,
for instance for the temperatures below 32 adding
progressively larger amounts of anti-freeze.
A cool tool to have outside a window in a science
classroom
to demonstrate the 3 states of matter visually.
Old version of this Idea
http://science.hows...com/question663.htm
[Vernon, Feb 08 2016]
eutectic
https://en.wikipedi...iki/Eutectic_system
Too busy to read this now but at first glance I have no idea what they're talking about. [doctorremulac3, Feb 08 2016]
Whoa... there are way more states of matter than I knew of.
https://en.wikipedi...of_states_of_matter
[2 fries shy of a happy meal, Feb 11 2016]
[link]
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Be sure to select* eutectic substances; otherwise, they will
have a range of temperatures at which they are partially
melted. |
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Wow. I always learn something coming to this site but
this one's a bit complicated. See link. |
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The important thing to understand is that a eutectic
substance doesn't have separate solidus and liquidus
temperatures. In other words, it will either be solid or
liquid at any given static temperature, not partly solid and
partly liquid. |
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I didn't actually know eutecticity (?) was as complicated as
that. |
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Intereshtingly, water/ethanol is eutectic at about
94% ethanol. I am convinced that this is nature's way
of telling us to make stronger cocktails. |
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//it will either be solid or liquid at any given static
temperature, not partly solid and partly liquid.// |
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So water for instance would get slushy before it froze
making its state a bit unclear. |
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Well that's certainly easier to understand than the
link I put up. |
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No, water has a definite freezing point. If you
lower its temperature below 0°C, it will become
completely solid - the slushy phase is just
transitory. |
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So water is inherently "eutectic" in that sense
(though the word isn't really appropriate). |
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On the other hand, if you cool seawater, which is
not eutectic, there is a temperature at which low-
salt ice will form, leaving a high-salt liquid; and
this will remain stable however long you leave it at
that temperature. |
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But if you take a ~20% solution of salt (which _is_
eutectic) and cool it to about -20°C, it will freeze
uniformly. |
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Eutecticism is important in alloys. A molten
eutectic alloy will cool and solidify as one,
whereas a non-eutectic alloy will drop out crystals
of one metal (or an alloy different from the overall
mix) as it cools, and then the remaining metal will
solidify at a lower temperature - which may or
may not be desirable. Solders and casting alloys
are often eutectic. |
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Is there some mixture of two substances that would
do the trick for this where you just change the ratio
to get freezing point/evaporation point you want? |
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I don't think so. If the mix isn't eutectic (meaning
that it has a particular ratio of components), it won't
have a defined freezing point. I think it's the same
for evaporation, which is why distillation works. |
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Ok, then you just use water and like I proposed just
have different pressure in each chamber, yes? |
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Ok no. After reading up on it I see that water reacts
weirdly under pressure with regard to its freezing
point but surely there's some
liquid that you could make freeze and boil when you
want it by putting the right amount of vacuum or
pressure in each chamber, ja? |
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Many acids have crazy phase diagrams with multiple eutectic points at different concentrations - maybe you could use that somehow? |
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Yea, I was hoping it would be something easier but
I think it could be done with a little work.
Wish I had time to put into fun stuff like this. |
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It would certainly be in interesting project. |
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Why bother with eutectics, though? There are
gaboojles of organic compounds, with melting
temperatures from wayyy subzero to the hundreds of
°C - just find set of relatively cheap and cheerful
ones with appropriate melting points. |
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This would be a cool science exhibit. Get several substances lined up and just change the temperature / pressure in the chamber and watch how they react. |
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The star of the show would be two substances, one that froze the other that boiled at the same temperature. I doubt there is such a thing but that would certainly be entertaining. |
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