HOW TO MAKE A THERMOMETER

Every body of us knows the use of thermometer. This is the simplest instrument to know whether some body is suffering from fever. Through this very simple instrument you can measure your body temperature which is above 98.4o F /37oC would clearly mean that you are suffering from fever. We also measure the room temperature by using thermometer.

                You can make a simple thermometer if you try using the following method.

Requirements

1.  A  narrow-necked  plastic or glass bottle.

2.    Tap water

3.  Methyl Alcohol       

4.    Food Colourant

5.    Clear, thin plastic straw

6.    Modeling Clay

  Take equal amount of water and methyl alcohol ( 50: 50 %), in a narrow –necked plastic/glass bottle so that it fills roughly a quarter of the bottle. Add a few drops of food colourant to it and gentle mix the contents. Insert the plastic straw in the bottle, taking care that the straw does not touch the bottom of the bottle. Do not suck through the straw since methyl alcohol is poisonous. Now   seal  the mouth of the bottle with some modeling clay without disturbing the position of the clay. Now you have prepared the working model of a thermometer.

Just notice the level of the coloured liquid in the straw. Now as you take your thermometer to the sun light , you would observe the coloured liquid move up through the straw. Why does this happen. This can be explained very simple. The coloured liquid contained in the bottle expanded on warming due t exposure to sun light  and hence made it rise through the straw.

Basically , a thermometer works on the principle of expansion and contraction of liquids with temperature rise. On heating , the liquids expand because the molecules move much faster and push against one another. On the other  hand, at low temperature, the molecules of a liquid move rather slowly and require less space which is why the liquid contracts. You can see clearly the rise and fall in the level of the coloured liquid in the straw with changes in temperature of the place where this thermometer is kept. If the temperature is very high, the liquid might come out of the straw and you have to become very careful.

You may be aware that temperature is normally measured in a scale called Fahrenheit and in Celsius/Centigrade . But do  you know how to change the temperature from  Celsius into Fahrenheit . Just multiply the number by 1.8 and add 32o to it.