Ethanol boils at 78°C. Why must thermometers used to measure 150°C or more contain mercury, which boils at 357°C?
Answers
I do not understand what you are asking.It is not a must but mercury thermometers are precise in that range of temps so it is more common
Answer:
:
The boiling point of ethanol is
+
78
∘
C
. This limits the top measurement of the thermometer to this temperature. Of course, the MELTING POINT of ethanol is
−
100
∘
C
or so, which allows measurement of temperatures lower than
0
∘
C
.
A thermometer may be filled with mercury, or (for lower temperatures), it may be filled with ethyl alcohol, toluene, xylenes, or some liquid whose melting point/boiling point extends the range of measurement. Because (as far as I know) the rate of liquid expansion when heated gives a LINEAR SCALE, the thermometer may be calibrated by placing in an ice bath (or a colder bath), marking off this freezing point, then placing in a bath of boiling water, and marking off this boiling point at
100
∘
C
. The THINNER the glass capillary, the greater the distance between the two points and the more accurate the reading on the thermometer.
Explanation:
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