what chapters in College Physics 2e openstax do i need to read to cover this content? Thermal Expansion and  Kinetic Theory

Copyright © 2009 Pearson Education, Inc. 

Thermal Expansion
Linear expansion 
occurs when an object  
is heated. 

Here, α is the coefficient of linear  
expansion. 
Copyright © 2009 Pearson Education, Inc. 
Thermal Expansion
Copyright © 2009 Pearson Education, Inc. 
Thermal Expansion 
Example: Bridge expansion.  
The steel bed of a suspension bridge is  200 m long at 20°C. If the extremes of  temperature to which it might be  exposed are -30°C to +40°C, how much  will it contract and expand?
Copyright © 2009 Pearson Education, Inc. 
Thermal Expansion 
Conceptual Example: Do holes expand or  contract? 
If you heat a thin, circular ring in the  oven, does the ring’s hole get larger or  smaller?
Copyright © 2009 Pearson Education, Inc. 
Thermal Expansion 
Example: Ring on a rod. 
An iron ring is to fit snugly on a  cylindrical iron rod. At 20°C, the diameter  of the rod is 6.445 cm and the inside  diameter of the ring is 6.420 cm. To slip  over the rod, the ring must be slightly  larger than the rod diameter by about  0.008 cm. To what temperature must the  ring be brought if its hole is to be large  enough so it will slip over the rod?
Copyright © 2009 Pearson Education, Inc. 
Thermal Expansion 
Conceptual Example: Opening a tight jar  lid. 
When the lid of a glass jar is tight,  holding the lid under hot water for a  short time will often make it easier to  open. Why?
Copyright © 2009 Pearson Education, Inc. 
Thermal Expansion
Volume expansion is similar, except that it is  relevant for liquids and gases as well as solids: 

Here, β is the coefficient of volume 
expansion. 
For uniform solids, β ≈ 3α. 
Copyright © 2009 Pearson Education, Inc. 
Thermal Expansion 
Example: Gas tank in the Sun. 
The 70-liter (L) steel gas tank of a car is  filled to the top with gasoline at 20°C.  The car sits in the Sun and the tank  reaches a temperature of 40°C (104°F).  How much gasoline do you expect to  overflow from the tank?
Copyright © 2009 Pearson Education, Inc. 

Thermal Expansion
Water behaves differently from most other solids—its  minimum volume occurs when its temperature is 4°C.  As it cools further, it expands, as anyone who leaves  
a bottle in the freezer to cool and then forgets about it  can testify. 
Copyright © 2009 Pearson Education, Inc. 

Atomic Theory of Matter
Atomic and molecular masses are measured in  unified atomic mass units (u). This unit is  defined so that the carbon-12 atom has a mass  of exactly 12.0000 u. Expressed in kilograms: 
1 u = 1.6605 x 10-27 kg. 
Brownian motion is the jittery  
motion of tiny flecks in water;  
these are the result of  
collisions with individual water  
molecules. 
Copyright © 2009 Pearson Education, Inc. 
Atomic Theory of Matter
On a microscopic 
scale, the  
arrangements of  
molecules in solids 
(a), liquids (b), and  
gases (c) are quite  
different. 
Copyright © 2009 Pearson Education, Inc. 
Atomic Theory of Matter 
Example: Distance between atoms. 
The density of copper is 8.9 x 103 kg/m3,  and each copper atom has a mass of 63 u.  Estimate the average distance between the  centers of neighboring copper atoms.
Copyright © 2009 Pearson Education, Inc. 
Thermal Equilibrium and the Zeroth  Law of Thermodynamics
Two objects placed in thermal contact will  eventually come to the same temperature.  When they do, we say they are in thermal  equilibrium. 
The zeroth law of thermodynamics says that if  two objects are each in equilibrium with a third object, they are also in thermal equilibrium with  each other. 
Copyright © 2009 Pearson Education, Inc. 

The Ideal Gas Law and the Molecular  Interpretation of TemperatureThe force exerted on the wall by  

the collision of one molecule is 

Then the force due to all 
molecules colliding with that  
wall is 

Copyright © 2009 Pearson Education, Inc. 
The Ideal Gas Law and the Molecular  Interpretation of Temperature
The averages of the squares of the speeds in all  three directions are equal: 

So the pressure is: 

Copyright © 2009 Pearson Education, Inc. 
The Ideal Gas Law and the Molecular  Interpretation of Temperature
Rewriting, 
so 

The average translational kinetic energy of  the molecules in an ideal gas is directly  proportional to the temperature of the gas. 
Copyright © 2009 Pearson Education, Inc. 
The Ideal Gas Law and the Molecular  Interpretation of Temperature
Example 18-1: Molecular kinetic energy. 
What is the average translational kinetic  energy of molecules in an ideal gas at 37° C? 
Copyright © 2009 Pearson Education, Inc. 
The Ideal Gas Law and the Molecular  Interpretation of Temperature
We can now calculate the average speed of  molecules in a gas as a function of  
temperature: 

Copyright © 2009 Pearson Education, Inc. 
Distribution of Molecular Speeds
The molecules in a gas will not all have the  same speed; their distribution of speeds is  called the Maxwell distribution: 


Copyright © 2009 Pearson Education, Inc. 

Distribution of Molecular Speeds
The Maxwell distribution depends only on  the absolute temperature. This figure shows  distributions for two different temperatures;  at the higher temperature, the whole curve  is shifted to the right. 

Copyright © 2009 Pearson Education, Inc.