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 can think about the process in terms of the Gibbs free energy equation. The Gibbs free energy change (∆G) is given by the equation:
∆G = ∆H - T∆S
where ∆H is the change in enthalpy, T is the temperature in Kelvin, and ∆S is the change in entropy.
In the case of the conversion of liquid water to ice, we are going from a more disordered state (liquid water) to a more ordered state (ice). This means that the change in entropy (∆S) is negative.
At temperatures above 0°C, the ∆H term (change in enthalpy) is positive because energy needs to be withdrawn from the system to convert liquid water into ice.
Since both the ∆H term and the ∆S term are negative, the overall sign of the change in free energy (∆G) is negative. Therefore, the answer is C. Negative.
To summarize, the conversion of liquid water to ice at temperatures above 0°C has a negative change in free energy.