Answer 1

When we heat an object, it expands, i.e. its volume increases.

Work done by the system, ΔW = P Δ V

Using the first law of thermodynamics, we get

ΔQ = ΔU + ΔW

Since the volume changes, ΔW has some non-zero positive value. Thus, heat given to the object is not equal to the increase in the internal energy of the system.