Ideally, when a thermometer is used to measure the temperature of an object, the

Question

Ideally, when a thermometer is used to measure the temperature of an object, the temperature of the object itself should not change. However, if a significant amount of heat flows from the object to the thermometer, the temperature will change. A thermometer has a mass of 26.0 g, a specific heat capacity of c = 815 J/(kg · C°), and a temperature of 12.0° C. It is immersed in 119 g of water, and the final temperature of the water and thermometer is 42.7° C. What was the temperature of the water before the insertion of the thermometer?

Explanation / Answer

The thermometer will absorbe a number of joules given by :-
Q1 = 0.026 kg * 815 j/(kg-C)*( 42.7-12)C = 650.53 J

Let us suppose that it will cool the water by dT.

So,dT = 650.53 J/[ 119 g x 1 cal/g/Cdeg x 4.184 J/cal] = 1.31 degree C
where, specific heat capacity of water= 4.184 J/cal

So the water temperature before the thermometer was inserted is:-
T= 42.7+1.31= 44.01 degree C.

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