Alcohol thermometer is preferred for a very cold region because its freezing point of alcohol is - 117°C.  So, it can measure the temperature of the very cold region.


Temperature of boiling water can’t be measured using an alcohol thermometer because the temperature of boiling water is at 100°C and that of alcohol is 78°C . So, alcohol boils before water and can’t be measured the boiling point of water.

Constriction presents in a clinical thermometer let the level of mercury increase when the temperature increases but doesn’t let it fall when temperature decreases and it helps to take the correct reading.

A clinical thermometer is jerked before using it to bring the level of mercury in the bulb.

Steel pointers are used in maximum and minimum thermometer to locate the temperature of the region.

Importance of thermometer are as follow:

  • A clinical thermometer is used in the clinic or home to measure the temperature of human body.
  • A laboratory thermometer is used in the laboratory to measure the temperature of a different substance.
  • Maximum and minimum thermometer is used to measure the maximum and minimum temperature of the region.

Thermometer is based on the principle of, ' when a body is heated it expands and when a body is cooled it contracts ’.

I use mercury thermometer to measure the temperature above 80°C because the boiling point of alcohol is 78°C . So, it can’t measure the temperature above 78°C.

Maximum and minimum thermometer is used when maximum and minimum temperature of a region is required.

The advantages of using alcohol instead of mercury in a thermometer are as follows:

  • The freezing point of alcohol is 117°C. Thus, it remains liquid to a very low temperature. Due to this reason alcohol thermometer is used for measuring the temperature in very cold regions.
  • Its expansion rate is about seven times more than that of mercury.

The advantage of using alcohol instead of mercury in a thermometer is as follows:

  • It is colorless. Hence, it should be colored before use in order to see it easily.
  • It is a bad conductor of heat.
  • It wets the wall of the capillary glass tube of the thermometer.
  • Its expansion rate is not uniform.
  • Its boiling point is 78°C. So, it can’t be used for measuring the temperature above 78°C. Due to this reason the alcohol thermometer is not used to measure temperature in very warm places.
  • It has low density.

I prefer to use laboratory thermometer to measure the temperature of boiling water.

I prefer to use clinical thermometer to measure the temperature of human body.

They are as follows:
  • It is a good conductor of heat.
  • It has uniform rate of expansion and contraction.
  • Mercury does not wet glass. So, the rise and the fall of the mercury in the tube is clean and smooth.
  • It has very high density, so a small bulb of a thermometer can contain much mercury.
  • Mercury remains liquid state over a quite wide range of temperature because it freezes at 39°C and boils at 357°C.

Solution,

\begin{align*} \frac {C - 0}{100} &= \frac {F-32}{180} \\ \text {Here,}\: F =98.6\: \text {Fahrenheit} \\\frac {(C- 0)} {100} &= \frac {(98.6- 32)}{180} \\\text {or,}\:\frac {C}{100} &= \frac {66.6}{180} \\ \text {or,}\: C \times 180 &= 66.6 \times 100\: ( \text {cross multiplication}) \\ \text {or,}\: C &= \frac {666}{18} = 37^o \:\text {Celsius} \\\end{align*}

Solution,

\begin{align*} \frac {C - 0}{100} &= \frac {F-32}{180} \\ \text {Here,}\: F = 0 \: \text {Fahrenheit} \\\frac {(C- 0)} {100} &= \frac {(0- 32)}{180} \\\text {or,}\:\frac {C}{100} &= \frac {-32}{180} \\ \text {or,}\: C \times 180 &= -32\times 100\: ( \text {cross multiplication}) \\ \text {or,}\: C &= \frac {-320}{18} = -17.7^o \:\text {Celsius} \\\end{align*}

Solution,

\begin{align*} \frac {F-32}{180} &= \frac {K-273}{180} \\ \text {Here,}\: F = 200\: \text {Fahrenheit} \\\frac {(200 - 32)} {180} &= \frac {(k- 273)}{100} \\\text {or,}\: K - 273 &= (200 - 32) \times \frac {100}{180} \\ \text {or,} \: k -273 &= (200 - 32) \times \frac {100}{180} \\ k &= 93.3 + 272 = 366.3 \\ \text {Thus,}\: 200\: \text {Farhrenheit} &= 366.6 \: \text {kelvin}\\\end{align*}

\begin{align*} \frac {C - 0}{100} &= \frac {k-273}{100} \\ \text {Here,}\: k = 100\: \text {kelvin} \\\frac {(C- 0)} {100} &= \frac {(100 -273)}{100} \\\text {or,}\: C - 0 &= \frac {-173\times 100}{100} \\ \text {or,}\: C &= -173 \\ \therefore 100\: \text {kelvin} = -173^o \:\text {Celsius} \\\end{align*}

Solution,

\begin{align*} \frac {C - 0}{100} &= \frac {F-32}{180} \\ \text {Here,}\: C = -40\: \text {Fahrenheit} \\\frac {(-40- 0)} {100} &= \frac {(F- 32)}{180} \\\text {or,}\:\frac {-40}{100} &= \frac {F -32}{180} \\ \text {or,}\: -40 \times 180 &= (F-32)\times 100\: ( \text {cross multiplication}) \\ \text {or,}\: F - 32 &= -4 \times 18 \\ \text {or,}\: F &= -40 \\ \therefore \text {The celcius and farenheit degree coincides when the value is}\: -40 \end{align*}

Solution

\begin{align*} \frac {C - 0}{100} &= \frac {K-273}{100} \\ \text {Here,}\: C =200\: \text {Fahrenheit} \\\frac {(200 - 0)} {100} &= \frac {(K-273)}{100} \\\text {or,}\: K - 273 &= 200 \\ \text {or,} \: K &= 200 + 273 \\ \text {or,}\: K &= 473\: \text {kelvin} \\ \therefore 200^o \text {is equal to}\: 473\: \text {kelvin}\\\end{align*}