A 0.50 kg steel sphere is heated from 350 K to 450 K while remaining solid. Which of the following correctly describes the change in entropy ΔS of the sphere and the primary reason for that change?
a) ΔS is negative because the internal energy of the sphere increases during heating.
b) ΔS is zero because the phase of the sphere is unchanged during heating.
c) ΔS is positive because greater thermal energy allows access to a larger number of vibrational states within the lattice.
d) ΔS is positive but negligible because the temperature change is small compared with the absolute temperature.