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# Chapter 11-2: How does temperature affect enthalpy and entropy? PowerPoint PPT Presentation

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.

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

### 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

• 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

• 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

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

• Mass was given, and not needed