S(T) = S(0) + ∫[C/T]dT (from 0 to T)

S(0) = S(20) - ∫[C/T]dT (from 0 to 20 K)

ΔS = ∫[0.1T/T]dT (from 5 to 10 K) = ∫0.1dT (from 5 to 10 K)

S(T) = S(0) + ∫[C/T]dT (from 0 to T)

Using the third law of thermodynamics, we can write:

ΔS = C * ln(10/5) = C * ln(2)

or

Using the third law of thermodynamics: