ENSC1004 - Lecture 16

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ENSC1004 - Lecture 15
Thermal Properties - Slides

Introduction

• Thermal property is a material’s response to the application of heat
  • As a solid absorbs heat, it expands

Heat Capacity

• When heated, a material experiences an increase in temperature:
  $\Delta Q=C\Delta T$
• See: Heating Processes

There are many different models for heat capacity:

Dulong-Petit Law (Classical View)

• Each atom has vibrations (energy = 3RT per mole)
• Predicts constant heat capacity
• Works well at room temperature
• Fails at low temperature

Einstein Model (Quantum View)

• Atoms vibrate like quantum oscillators
• Vibrations happen in “packets” of energy
• Explains why heat capacity drops at low T

Debye’s Model

• Relaxes assumption that all atoms vibrate at the same frequency
• Matches experimental results very well
• As verry low T: $Cv\propto T^3$
• At high T: $Cv\approx 3R$

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ENSC1004 - Lecture 17