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.
-- doctorremulac3, Feb 08 2016

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]

Be sure to select* eutectic substances; otherwise, they will have a range of temperatures at which they are partially melted.

*plural
-- notexactly, Feb 08 2016


//eutectic //

Wow. I always learn something coming to this site but this one's a bit complicated. See link.
-- doctorremulac3, Feb 08 2016


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.

I didn't actually know eutecticity (?) was as complicated as that.
-- notexactly, Feb 08 2016


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.
-- MaxwellBuchanan, Feb 08 2016


//it will either be solid or liquid at any given static temperature, not partly solid and partly liquid.//

So water for instance would get slushy before it froze making its state a bit unclear.

Well that's certainly easier to understand than the link I put up.
-- doctorremulac3, Feb 08 2016


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.

So water is inherently "eutectic" in that sense (though the word isn't really appropriate).

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.

But if you take a ~20% solution of salt (which _is_ eutectic) and cool it to about -20°C, it will freeze uniformly.

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.
-- MaxwellBuchanan, Feb 08 2016


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?
-- doctorremulac3, Feb 08 2016


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.
-- MaxwellBuchanan, Feb 08 2016


Ok, then you just use water and like I proposed just have different pressure in each chamber, yes?

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?
-- doctorremulac3, Feb 09 2016


Many acids have crazy phase diagrams with multiple eutectic points at different concentrations - maybe you could use that somehow?
-- mitxela, Feb 10 2016


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.

It would certainly be in interesting project.
-- doctorremulac3, Feb 10 2016


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.
-- MaxwellBuchanan, Feb 10 2016


Re: Link.

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.

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.
-- doctorremulac3, Feb 11 2016



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