Answer
(a) positive.
(b) negative.
(c) negative.
Work Step by Step
(a) Melting results in increased mobility and randomness. Therefore entropy increases and $\Delta S_{sys}$ is positive.
(b) As the change is from aqueous state to solid-state, entropy decreases. $\Delta S_{sys}$ is negative.
(c) Condensation results in decreased mobility and randomness. Therefore, entropy decreases and $\Delta S_{sys}$ is negative.
