Slope of Coexistence Curve Formula:
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Definition: The slope of the coexistence curve (dP/dT) represents how pressure changes with temperature along the phase boundary between two phases of matter.
Purpose: This calculator determines the slope using the Clausius-Clapeyron equation, which relates the slope to entropy and volume changes during phase transitions.
The calculator uses the formula:
Where:
Explanation: The slope is calculated by dividing the entropy change by the volume change during the phase transition.
Details: Understanding this slope helps predict phase behavior, design phase-change materials, and analyze thermodynamic systems.
Tips: Enter the entropy change (ΔS) in J/K and volume change (ΔV) in m³. Both values must be positive.
Q1: What does a positive slope indicate?
A: A positive slope (most common) means the higher-temperature phase has higher entropy and larger volume.
Q2: What about water's anomalous behavior?
A: For water's liquid-solid transition, ΔV is negative (ice expands), resulting in a negative slope.
Q3: How precise should my input values be?
A: Use at least 3-4 significant figures for meaningful results in most applications.
Q4: What units should I use?
A: Use SI units - J/K for entropy and m³ for volume. The result will be in Pa/K.
Q5: Can this be used for all phase transitions?
A: Yes, it applies to any first-order phase transition (liquid-vapor, solid-liquid, etc.).