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phy131studiof15:lectures:chapter21 [2015/11/18 09:20]
mdawber [Molar Specific Heat for Gases]
phy131studiof15:lectures:chapter21 [2015/11/18 09:21]
mdawber [Vibrational degrees of freedom]
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 ===== Molar Specific Heat for Gases ===== ===== Molar Specific Heat for Gases =====
  
-We previously introduced the [[phy141:​lectures:​35&#​specific_heat_capacity|specific heat]] which gives the [[wp>​Heat_capacity|heat capacity]] heat capacity of a material per unit mass. Here we will use molar specific heats for gases at constant pressure $c_{P,m}$ and constant volume $c_{V,m}$ and explain the difference between these on the basis of the first law of thermodynamics.+We previously introduced the specific heat which gives the [[wp>​Heat_capacity|heat capacity]] heat capacity of a material per unit mass. Here we will use molar specific heats for gases at constant pressure $c_{P,m}$ and constant volume $c_{V,m}$ and explain the difference between these on the basis of the first law of thermodynamics.
  
 If we increase the temperature of a gas by $\Delta T$ at constant volume $Q_{V}$ then the first law tells us that  If we increase the temperature of a gas by $\Delta T$ at constant volume $Q_{V}$ then the first law tells us that 
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 ===== Vibrational degrees of freedom ===== ===== Vibrational degrees of freedom =====
  
-As well as moving and rotating molecules can vibrate. However these modes are typically "​frozen out" in simple molecules at room temperature. As molecules get more complicated the vibrational modes start to contribute to the specific heat. If we cool a gas down we can the rotational degrees of freedom in gas can also become frozen. Quantum theory is required to explain why the number of active modes is dependent on temperature!+As well as moving and rotating molecules can vibrate. However these modes are typically "​frozen out" in simple molecules at room temperature. As molecules get more complicated the vibrational modes start to contribute to the specific heat. If we cool a gas down the rotational degrees of freedom in gas can also become frozen. Quantum theory is required to explain why the number of active modes is dependent on temperature!
  
 {{DiatomicSpecHeat1.png?​600}} {{DiatomicSpecHeat1.png?​600}}
phy131studiof15/lectures/chapter21.txt ยท Last modified: 2015/11/18 09:21 by mdawber
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