Question

Predict whether the changes in enthalpy, entropy, and free energy will be positive or negative for the melting of ice, and explain your predictions. How does temperature affect the spontaneity of this process?

Answer 1

The equation that brings together enthalpy (H), entropy (S) and free energy is Gibb's free energy.

\[\Delta G = \Delta H - T \Delta S \]

If G is smaller than 0, the reaction is favoured and spontaneous.
If G is 0, well it is in eqilibrium
If G is bigger 0, the reaction is not spontaneous.

Delta H here is the amount of heat the reaction absorbs, in this case, to melt ice, which is given by the enthalpy of fusion, a positive quantity.

The higher the value of entropy S, the higher the degree of disorder.
When I melt ice, the ordered arrangements of the ice crystals break into the dancing water molecules, and thus disorder increases. This means that delta S is a positive quantity.

Dumping this into gibbs free energy, with the increasing temperature, H remains the same but TdeltaS becomes more negative, and delta G becomes more negative and thus the reaction is more energetically favoured.

Answer 2

what's a simplier way this can be put

Answer 3

delta G is negative because the reaction is spontaneous (happens naturally)
delta H is positive because you need to supply heat for the reaction to occur.
delta S is postive because the amount of disorder of the system increases
If T increases, delta G becomes more negative as TdeltaS becomes more negative. and the reaction becomes more spontaneous, if that makes any sense.

Answer 4

thanks