Volume change when liquid goes to solid.

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Discussion Overview

The discussion revolves around understanding the volume change that occurs when a liquid transitions to a solid state, specifically focusing on water turning into ice. Participants explore the theoretical and practical aspects of deriving an equation to predict this volume increase based on known densities and thermodynamic principles.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant seeks assistance in deriving an equation for the volume increase when a liquid solidifies, given its density.
  • Another participant notes that most liquids decrease in volume upon solidification, with water being a notable exception, suggesting that specific material properties must be referenced for accurate predictions.
  • A follow-up inquiry asks for a simplified method to derive an equation specifically for water transitioning to ice.
  • A participant discusses the relevance of the pressure-temperature diagram and the entropy change during the phase transition, indicating that knowledge of transition temperature and specific heat of fusion could aid in understanding the energy involved in volume change, although they express difficulty in deriving this relationship.

Areas of Agreement / Disagreement

Participants acknowledge that water behaves differently than most liquids during solidification, but there is no consensus on a specific method or equation for predicting the volume change, and the discussion remains unresolved.

Contextual Notes

Participants mention the need for specific material properties and thermodynamic principles, indicating that assumptions about pressure and temperature conditions may affect the derivation process.

ladil
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Hello!

I need some help regarding a simple matter...

How do I derive an equation for the increase in volume when a liquid goes to a solid state when I know the density of the liquid?
 
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Most liquids reduce volume when they become solid. Water is one of the very few exceptions. Between the enthalpy of fusion and pressure-temperature diagram, you might be able to get an estimate, but generally, density change at phase transition is something you need to look up for specific material.
 
ok. Thanks for the help. Ill check it out.
Lets say it is water that becomes ice. Is there any easy way to derive an equation for predicting the increase in volume?
 
The slope of the PT diagram should tell you how much the entropy changes at transition, and knowing transition temperature and specific heat of fusion, you should be able to figure out how much energy goes into volume changed at given pressure, which should give you the density change. But I'm having a bit of trouble deriving this. Sorry, thermodynamics has never been my strong field.
 

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