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

2. 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

3. 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

4. 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

5. Temperature Affects Molar Enthalpy

6. How much does the molar enthalpy change when a 92.3g block of ice is cooled from -0.2 ⁰ C to -5.4 ⁰ C?

7. Things to Notice about that Problem Mass was given, and not needed Scientists often find themselves with more information than needed Δ T = T f – T i --- 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

8. Changes of State

9. Homework/Rest of Class Work on problems 9-13 on page 395