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.

Answer 1

For the answer to the question above,

322Joules of heat energy is added to the system (gold bar) while no work is done on the gold bar, this is an isochoric/isovolumetric process, thus 
ΔU = 322J + 0 
=322J 
Therefore the internal energy increase by 322J
I hope my answer helped you.