Change in Entropy:

$\overline{){\mathbf{\u2206}}{\mathbf{S}}{\mathbf{=}}\frac{\mathbf{\u2206}\mathbf{Q}}{\mathbf{T}}}$

The net change in entropy:

$\overline{){\mathbf{\u2206}}{{\mathbf{S}}}_{\mathbf{s}\mathbf{y}\mathbf{s}}{\mathbf{=}}{\mathbf{\u2206}}{{\mathbf{S}}}_{{\mathbf{1}}}{\mathbf{+}}{\mathbf{\u2206}}{{\mathbf{S}}}_{{\mathbf{2}}}}$

a. An object at 400 K absorbs 25.0 kJ of heat from the surroundings. What is the change in entropy Δ*S* of the object? Assume that the temperature of the object does not change appreciably in the process. Express your answer numerically in joules per kelvin.

b. Two objects form a closed system. One object, which is at 400 K, absorbs 25.0 kJ of heat from the other object, which is at 500 K. What is the *net* change in entropy Δ*S*_{sys} of the system? Assume that the temperatures of the objects do not change appreciably in the process. Express your answer numerically in joules per kelvin.

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