Question

Melting of ice is a spontaneous reaction at room temperature and pressure because melting is accompanied by _____.

Answer 1

Answer:

An increase in entropy

Explanation:

In ice, the molecules are very well ordered because of the H-bonds. As ice melts, the intermolecular forces are broken (requires energy), but the order is interrupted (so entropy increases). Water is more random than ice, so ice spontaneously melts at room temperature.

Just think about this rationally. Melting ice (or anything) will require heat put in (this is called the latent heat of fusion), so you automatically know that the change in enthalpy is going to be positive. In order to make the reaction spontaneous, delta G, the Gibbs free energy has to be negative. So now look at the formula Delta(G) = Delta(H) - T*Delta*(S). If you know that g is negative, and H is positive, then it is only possible if -T*Delta(S) is negative. If that is positive, then Delta(S) has to be positive. So theres your answer :). An increase in entropy