Phase Change Problems: How to Solve for Heat Release and Temperature Changes

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SUMMARY

This discussion focuses on solving phase change problems related to heat release and temperature changes in thermodynamics. The specific questions involve calculating heat release during the freezing of steam, condensing steam, and the cooling of water with ice. Key equations utilized include the change in heat formula: ΔHeat = mass * specific heat * change in temperature and ΔHeat = mass * latent heat. The solutions require substituting known values into these equations to find the desired results.

PREREQUISITES
  • Understanding of thermodynamic principles, specifically phase changes.
  • Familiarity with specific heat capacity and latent heat concepts.
  • Ability to perform calculations involving mass and temperature changes.
  • Knowledge of the properties of water and steam at various temperatures.
NEXT STEPS
  • Study the specific heat capacities of water and ice for accurate calculations.
  • Learn about latent heat of fusion and vaporization for phase change problems.
  • Practice solving additional thermodynamic problems involving heat transfer.
  • Explore the concept of thermal equilibrium in mixed-phase systems.
USEFUL FOR

Students preparing for exams in thermodynamics, educators teaching phase change concepts, and anyone needing to understand heat transfer in physical chemistry.

lolphysics3
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Homework Statement



I have three questions I need help on. Can someone please explain to me how to do them, how to correctly set up the problem, and what I need to know. I have a test tomorrow. Thanks!

Q1: How much heat is released freezing 75 grams of steam at 110 degrees C into ice at -5.1 degrees C

Q2: How much heat is released in condensing 43 grams of steam at 100 degrees C and then cooling the water to 20 degrees C.

Q3: I make a cup of tea with 43 g of water at 99 degrees C. To cool it, I add 5.1g of ice at 0 degrees C. By how much will the temperature of the tea come down by once I add the ice? (Treat tea the same as regular water)



Homework Equations



Change in Heat= mass*specific heat*change in temperature
Change in Heat=mass*latent heat




The Attempt at a Solution

 
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Q1 is straight forward. Just use the first equation you posted.

\Delta Heat = m (Cp) ( \Delta Temp)

Cp is specific to the material and you can look it up for homework and will most likely be provided for tests.

Q2 is the same as Q1. Let me know if you don't understand the first two. It should just be plugging in numbers for each variable with change in temperature equal to final temp minus the starting temp.

Q3 I don't remember.
 

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