PHY 2002/II/21

I don't have the question in hand, but I think I could understand the experimental process from your question.

The experiment involves the transfer of a hot metal block, which was first dipped in hot water, to a cup of cold water. The specific heat capacity of the metal was then calculated by recording the temperature rise of the cold water, together with the decrease in temperature of the metal block.

Using the heat balance equation, assume no heat loss,
MCT = mcT'
where M and m are the masses of the metal block and cold water respectively
T and T' are the temperature changes of the metal block and cold water respectively
C and c are the specific heat capacities of the metal block and cold water respectively

thus, C = mcT'/MT ---------------------- (1)

Statement (A): if there is hot water adhere to the metal block, this would give some heat to the cold water when the block is immersed in it. The heat balance equation now becomes,

MCT + Q = mcT'
where Q is the heat given out by the adhered hot water to the cold water (remember that the left hand side of the equation is the "heat loss", and the right hand side is the "heat gain")

thus, C = (mcT' - Q)/MT -------------------- (2)

Apparently, the value of the term (mcT' - Q) is smaller than the term mcT' given in equation (1). The value of C in equation (2) is thus
smaller than that in equation (1), which is the experimental value.
In other words, the experimental value is higher than the true value.
Statement (B)
For similar reason, the heat balance equation becomes,
MCT = mcT' + Q', where Q' is the heat gained by the surrounding air
C = (mcT'+Q')/MT
Compare this with equation (1), you should know the reason why the experimental value is now lower than the true value.

Statement (C):
The heat balance equation is similar to that in statement (B).