The discussion revolves around calculating the specific entropy of ice, with participants exploring the relationship between the latent heat of fusion and temperature. The original poster seeks clarification on the specific entropy value for ice compared to water.
Multiple interpretations of the calculations are being explored, with some participants providing guidance on unit consistency and the need for conversions between different measurement systems. There is no explicit consensus on the correct specific entropy value for ice at this stage.
Participants note discrepancies in the values used for latent heat and the need to clarify whether calculations should be performed in terms of kilograms or moles. There is an emphasis on ensuring that units match throughout the calculations.
Mapes said:Hi physics_newbi, welcome to PF. The decrease in entropy when a liquid freezes is \frac{L}{T}, where L is the latent heat (J/kg) and T is the freezing temperature (K). This will help you approximate the entropy of ice near the freezing point.
Mapes said:1) Your latent heat is off by several orders of magnitude.
2) You need to subtract \frac{L}{T} from the entropy of water at 0°C, which is actually 63.3 J/K-mol (you had the value at STP).
3) Some values are in kilograms and some are in moles, so you will want to convert everything to one or another.
Mapes said:Try to carry the units along with every number. If the units don't match up, then the calculation is invalid. The calculation
63.3\,\frac{\mathrm{J}}{\mathrm{K}\cdot \mathrm{mol}} - 1223\,\frac{\mathrm{J}}{\mathrm{K}\cdot \mathrm{kg}} = \dots
cannot give any meaningful answer.
The number of grams in a mole of a substance is its molecular weight.