at a temperature below 0 °C. Note that water is unusual in that its change in volume upon melting is negative. We can assume and substituting in (latent heat of fusion for water), K (absolute temperature), (change in specific volume from solid to liquid), we obtain To provide a rough example of how much pressure this is, to melt ice at −7 °C (the temperature many ice skating rinks are set at) would require balancing a small car (mass ~ 1000 kg) on a thimble (area ~ 1 cm2). Second derivative While the Clausius–Clapeyron relation gives the slope of the coexistence curve, it does not provide any information about its curvature or second derivative. The second derivative of the coexistence curve of phases 1 and 2 is given by where subscripts 1 and 2 denote the different phases, is the specific heat capacity at constant pressure, is the thermal expansion coefficient, and is the isothermal compressibility. See also Van 't Hoff equation Antoine equation Lee–Kesler method References Bibliography Notes Thermodynamic equations Atmospheric thermodynamics Engineering thermodynamics