Chapter Summary
11.1 Temperature
- Temperature is the quantity measured by a thermometer.
- Temperature is related to the average kinetic energy of atoms and molecules in a system.
- Absolute zero is the temperature at which there is no molecular motion.
- There are three main temperature scales: Celsius, Fahrenheit, and Kelvin.
- Temperatures on one scale can be converted to temperatures on another scale using the following equations:
[latex]T_{º \text{F}} = \frac{9}{5} T_{º \text{C}} + \text{32}[/latex][latex]T_{º \text{C}} = \frac{5}{9} \left(T_{º \text{F}} - \text{32}\right)[/latex][latex]T_{\text{K}} = T_{º \text{C}} + \text{273} . \text{15}[/latex][latex]T_{º \text{C}} = T_{\text{K}} - \text{273} . \text{15}[/latex]
- Systems are in thermal equilibrium when they have the same temperature.
- Thermal equilibrium occurs when two bodies are in contact with each other and can freely exchange energy.
- The zeroth law of thermodynamics states that when two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system, C, then A is also in thermal equilibrium with C.
11.2 Thermal Expansion of Solids and Liquids
- Thermal expansion is the increase, or decrease, of the size (length, area, or volume) of a body due to a change in temperature.
- Thermal expansion is large for gases, and relatively small, but not negligible, for liquids and solids.
- Linear thermal expansion is
[latex]\Delta L = αL \Delta T ,[/latex]
where [latex]\Delta L[/latex] is the change in length [latex]L[/latex], [latex]\Delta T[/latex] is the change in temperature, and [latex]\alpha[/latex] is the coefficient of linear expansion, which varies slightly with temperature.
- The change in area due to thermal expansion is
[latex]\Delta A = 2 αA \Delta T ,[/latex]
where [latex]\Delta A[/latex] is the change in area.
- The change in volume due to thermal expansion is
[latex]\Delta V = βV \Delta T ,[/latex]
where [latex]\beta[/latex] is the coefficient of volume expansion and [latex]\beta \approx 3α[/latex]. Thermal stress is created when thermal expansion is constrained.
“Section Summary” from College Physics 2e by OpenStax is licensed under a Creative Commons Attribution 4.0 International License.
