Past exam of the medicine course of the University of Oxford / 1867 / First examination / Physics / 9

Define the specific heat of a body.

If 100 grammes of iron be boiled for some time in water, when the height of the barometer is 760 m.m., and be then quickly transferred to a vessel containing 150 grammes of water at $10^{\circ }$C, what will be the common temperature of the iron and water ? It being assumed that no heat is lost, that a gramme of hot water adheres to the iron when it is transferred to the cold water, and that the specific heat of iron is 0.114.

Specific heat capacity is heat capacity per unit mass. For a specified thermodynamic process without a phase transition,The constraint matters: constant-pressure and constant-volume heat capacities need not coincide. Here the supplied iron value and water value are treated as constants.

At the stipulated barometer reading, iron left in boiling water reaches $100^{\circ }\mathrm{C}$. Taking water's specific heat capacity as one in the given units, the iron has heat capacity $100(0.114)=11.4$. The adhering gramme of hot water adds another one. Thus the hot material has total heat capacity $12.4$, compared with $150$ for the initially cool water.

The no-loss calorimetry energy balance issoThe adhering water enters on the hot side, not as extra water initially at $10^{\circ }\mathrm{C}$. The vessel's heat capacity is neglected, as none is supplied.