Question

If the maximum recorded temperature is used, rather than the extrapolated temperature, will the measured specific heat capacity of the metal be higher or lower than the real value? Explain. (Coffee Cup Calorimetry)

Answer 1

In a coffee cup calorimetry experiment, specific heat is calculated with the help of the quantity of heat supplied or used and the change in temperature recorded using the equation:

Q=mcΔT

where,

Q = quantity of heat supplied/used

m = mass of metal/element/ substance for which the specific heat is to be determined

c = specific heat of that substance

ΔT = change in temperature of that substance

Now, in this process, we plot the temperature with time to find out the final change in temperature but as the calorimeter is not perfectly insulated heat is constantly being lost to the surroundings giving the final temperature lower than that would have been if the calorimeter was perfectly insulated. Therefore, we extrapolate this time-temperature graph to find out the actual final temperature.

If we miss this extrapolation, we are actually considering a lower final temperature in our calculation than it should be ideally giving a smaller value of ΔT. As other quantities, such as Q and m are fixed in the equation, for a lower value of ΔT we'll get a higher value of c (specific heat) for the metal than its actual value.