Question

When ice melts at \[{1^o}C\]:
A. An increase in entropy
B. A decrease in enthalpy
C. A decrease in free energy
D. Process is spontaneous

Answer 1

Hint: When ice melts, it means solid is converting into liquid so the entropy of the system increases and the process becomes spontaneous. Due to spontaneity the free energy becomes negative at this point so we can say it decreases.

Complete step-by-step answer:
Ice is a solid, whose molecules have a crystal structure. This type of structure possesses strong bonds between molecules, thus leading to a really smooth movement of the molecules. Whereas water is a liquid, whose molecules are in layer form, not in a crystal structure, such that they freely move up and down. Molecules do not share the same bonds and result in a faster and more chaotic movement, than that in ice.
When ice melts at \[{1^o}C\], all of the given energy or heat is used to break those strong hydrogen bonds. So, when the bonds break due to heat, we can notice that the temperature doesn’t change, so the one part of the internal energy doesn’t change.
But the molecules start vibrating and moving randomly here and there due to no more restriction, the entropy or randomness of the system increases. This tells us that the system is spontaneous as well. We know that for a spontaneous process, the value of free energy is negative. Therefore, free energy decreases when ice melts.
But the enthalpy is positive or increases because heat is absorbed when bonds break and the process is endothermic. This is called enthalpy of fusion.

Hence, the correct options are (A), (C) and (D).

Note: If there is an increase in ambient temperature around a piece of ice, the temperature of the ice rises. But this steady increase in temperature stops as soon as the ice reaches its melting point because the ice turns into liquid water, and its temperature won't change until all of it has melted.