Chapter 11 2 how does temperature affect enthalpy and entropy
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Chapter 11-2: How does temperature affect enthalpy and entropy?. Thermodynamics Properties. Thermodynamics deals with energy transformation of several different kinds The three properties that affect the relationship between energy and matter are: Entropy Enthalpy Gibbs Energy.

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Chapter 11-2: How does temperature affect enthalpy and entropy?

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Chapter 11 2 how does temperature affect enthalpy and entropy

Chapter 11-2: How does temperature affect enthalpy and entropy?


Thermodynamics properties

Thermodynamics Properties

  • Thermodynamics deals with energy transformation of several different kinds

  • The three properties that affect the relationship between energy and matter are:

    • Entropy

    • Enthalpy

    • Gibbs Energy


Enthalpy h

Enthalpy (H):

  • Enthalpy can be thought of as heat or thermal energy = as something is heated the increase in enthalpy is equal to the thermal energy it receives

  • A change in enthalpy can be measured when a substance is heated and cooled, however enthalpy itself cannot be measured. So scientists have decided to assign all elements under standard conditions a molar enthalpy of zero


Properties

Properties

  • Extensive Properties – a property that depends on the amount of material present

    • Mass

    • Volume

    • Heat capacity

    • Enthalpy

    • Entropy

  • Intensive Properties – a property that does not depend on the amount of material present

    • Density

    • Pressure

    • Temperature

    • Concentration


Temperature affects molar enthalpy

Temperature Affects Molar Enthalpy

  • Enthalpy increase is equal to the heat input

    • So molar enthalpy can be found by dividing the enthalpy increase by the number of moles

  • Temperature also affects entropy because entropy can be directly measured


Chapter 11 2 how does temperature affect enthalpy and entropy

How much does the molar enthalpy change when a 92.3g block of ice is cooled from -0.2⁰C to -5.4⁰C?


Things to notice about that problem

Things to Notice about that Problem

  • Mass was given, and not needed

    • Scientists often find themselves with more information than needed

  • ΔT = Tf – Ti --- Gives the same result whether or not you change Celsius to Kelvin

    • In thermodynamics problems it doesn’t always work out this way so getting into the habit of changing the temperature to kelvin


Changes of state

Changes of State


Homework rest of class

Homework/Rest of Class

Work on problems 9-13 on page 395


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