Calculate the change in internal energy of the following system: A 100.0-g bar of gold is heated from 25°C to 50°C during which it absorbs 322 J of heat. Assume

Question

Calculate the change in internal energy of the following system: A 100.0-g bar of gold is heated from 25°C to 50°C during which it absorbs 322 J of heat. Assume the volume of the gold bar remains constant.
Express your answer to three significant figures and include the appropriate units.

Answer 1

For gold, specific heat at constant pressure (C_p) is tabulated as

129 Joules Per Kilogram Per Degree Celsius (J/kg • ºC).

For solid elements, it is said to be very hard to keep volume constant

under changing temperature; for this reason constant-volume specific

heat (C_v) is not usually tabulated for solids and liquids and the difference

between C_p & C_v is almost always tiny.

One here would then construct the change in internal energy sought as

ΔU equal to (U₂ − U₁) or mC_p(T₂ − T₁) or (0.1 kg)(129 J/kg • ºC)(50ºC − 25ºC)

which goes to 322.5 Joules.