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Why is when that alcohol and water mixed together the total volume is lesser?

Which liquid (water, alcohol, or mixed) is supposed to rise or lower when the temp. decreases or increases?

  • Doing my sci fair project iz due rly soon!!! aaaaahhh!!!! anyway i made 3 thermometers (homemade) one with alcohol & water together and another w/ just water & another w/ just alcohol. i put them in a hot pan expectin the alcohol 1 to rise the most but the water rose out of the top (literally). i really confuzed!!! help!!! does water change volume when the temperature changes?

  • Answer:

    The density of any material changes at different temperatures. Also remember that you absolutely cannot use water to measure temperatures above (or near) 100 degrees celcius, since that's where water boils. Assuming your alcohol is ethanol, its boiling point would be 78.3 Celcius. The boiling point of a mixture of miscible liquids is between the two individual boiling points, according to the link below. So your pure water thermometer, I would expect, would measure the highest temperature actually, BUT... . I think the answer is the expansivity (thermal expansion properties) of water. According to the second link below, water's expansivity coefficient increases quickly at rising temperatures and is much higher than ethanol's at higher temperatures. I guess the answer is simple. Your water is expanding too quickly to be useful as a temperature-measuring fluid. It might be useful for a very narrow temperature range, since it is so sensitive, but it looks like alcohol will allow a much greater range of measurements. Also, I assume that alcohol will rise the least, water the most, and a mixture of the two will rise somewhere in between. If the alcohol doesn't rise enough, try mixing in a bit of water.

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Well, all liquides expand as temperature rizes. Just some more than others. I think that the water began to boil in your case, and the alcohol just evaporated.

CrashBoy

Water changes volume/freezes... but yeah, the alcohol should have risen more. Hmmm- make sure you labeled the thermometers correctly. In fact, just try it again, it won't take very long :)

smrflt

It gets larger when frozen, and expanse it to vapor when heated.

Earth to Mars

Alcohol boils at a really low temperature - about 70C if i remember correctly. This is why you should never let gluehwein boil too long. It boils all the alcohol away. This is what happened to your thermometer. It will be great for measuring low temps - below freezing as alcohol has a low freezing point

rosie recipe

water increases temp. alcohol decreases temp. if you mix 2, alcohol will just evaporate.

zsarrone

All 3 thermometers should "increase in volume" as the temperature goes up. It is called Thermal Expasnsion. Most comercial thermometers (the red liquid inside of them) are actually dyed alcohol thermometers. *was the liquid in the pan boiling & was it water itself* If so wouldnt one imagine a thermometer of just watertoo would become heated to the point that it also would boil? *check the boiling points & freezing points of a variety of liquids to see if there are different substances which are better suited for different temerature ranges. (ie water is from 0 C to 100C, but isopropyl alcohol (rubbing alcohol) is from -89C to 82C, then there are mercury thermometers which are good from -38C to 356C *for high temerature ranges)

beanie_boy_007

In addition to guys above: Just notice that water has minimal volume at 4°C; rising or decreasing temperature will result in expansion.

(Φ)kaksi_guy

Many substances (including water and alcohol) will expand when heated.

Mark M

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