At temperatures above 0°C, what is the sign of the change in free energy for the conversion of liquid water to ice?
A. Positive
B. Zero
C. Negative
D. Not known
To determine the sign of the change in free energy for the conversion of liquid water to ice at temperatures above 0°C, we need to consider the equation for free energy change, which is given by:
ΔG = ΔH - TΔS
ΔG represents the change in free energy, ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy.
At temperatures above 0°C, liquid water is already in its stable state, and converting it to ice would involve a decrease in entropy. Since entropy tends to increase, a decrease in entropy (ΔS < 0) would result in a positive value for the second term (TΔS) in the free energy equation.
On the other hand, the enthalpy change (ΔH) for the conversion of liquid water to ice is negative, as energy is released during the process.
Therefore, the sign of the change in free energy (ΔG) would be determined by the balance between the negative enthalpy change and the positive term due to the decrease in entropy. Since the decrease in entropy at temperatures above 0°C dominates, the overall change in free energy (ΔG) would be positive.
Therefore, the answer is A. Positive.