A water thermometer would act in very much the
same way as a mercury thermometer. However if it is just a simple capillary tube with water
in it it must first be calibrated. This means it must be put in regions of known temperature.
However there is a slight problem with water as compared with mercury.
With a
mercury thermometer it would be placed first in melting ice and then in steam and the
position of the mercury thread at both temperatures marked. The interval between them on
the thermometer stem would then be divided into a hundred parts – each of these being one
degree Celsius.
However water boils at a 100 oC and freezes at 0 oC so the upper
and lower fixed points could not be used for a water thermometer. You would have to use a
mercury thermometer to measure the temperatures of two beakers of water at say 10 oC and
50 oC and then use these to calibrate your water thermometer.
There is another
problem with water – there will be a great deal of evaporation although at the temperature of
your hand this should not be too significant.