Thermodynamic Changes in Phase Transitions

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SUMMARY

The discussion focuses on thermodynamic changes during phase transitions, specifically analyzing the internal energy (U), heat transfer (Q), and work done (W) in four scenarios: (a) water freezing to ice, (b) ice melting to water, (c) water evaporating, and (d) water boiling. For water freezing to ice, internal energy decreases (delta U < 0), heat is released (delta Q < 0), and work done is negligible (delta W = 0). The participants confirm that similar analyses apply to the other phase transitions, emphasizing the relationship defined by the First Law of Thermodynamics (U = Q + W).

PREREQUISITES
  • Understanding of the First Law of Thermodynamics
  • Knowledge of phase transitions in thermodynamics
  • Familiarity with concepts of internal energy, heat transfer, and work
  • Basic grasp of thermodynamic equations and their applications
NEXT STEPS
  • Study the implications of the First Law of Thermodynamics in various phase transitions
  • Explore the concept of latent heat in phase changes
  • Investigate the role of pressure in phase transitions of water
  • Learn about the thermodynamic properties of different substances during phase changes
USEFUL FOR

Students studying thermodynamics, educators teaching phase transitions, and professionals in fields requiring thermodynamic analysis, such as chemical engineering and physical sciences.

kram
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Homework Statement


Does the internal energy increase/decrease(U), quantity of heat released or supplied (Q), and work done by or on a system (W) when
(a) water freezes to ice at constant temperature
(b) ice melts to water at constant temperature
(c) water evaporates at constant temperature
(d) water boils at constant temperature?


Homework Equations


First Law of Thermodynamics
U = Q + W
where U is internal energy of the system, Q is the quantity supplied to the system and W is the work done on the system.
 
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Not sure what the question is. I'm guessing, you are supposed to say whether deltaU, Q, and W is positive or negative or zero in each situation?

To answer the deltaU part, you need to remember that internal energy is a direct function of temperature.
 
Sorry, the question was asking whether deltaU, Q, and W is positive or negative or zero in each situation?

if (a) water freezes to ice at constant temperature,
then delta W = 0 (since work done by atmospheric pressure is negligible as volume change is small), delta Q < 0 (heat energy is released when bonds are formed during freezing) and hence by equation delta U = delta Q + delta W, delta U < 0 , ie internal energy decreases. am i right?

how about the others?
 

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