1: Gases and Equations of State
- Page ID
- 453420
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- 1.2: The Zeroth Law of Thermodynamics
- How does one use or measure temperature? Fortunately, there is a simple and intuitive relationship which can be used to design a thermometer – a device to be used to measure temperature and temperature changes. The zeroth law of thermodynamics can be stated as follows: If a system A is in thermal equilibrium with a system B, which is also in thermal equilibrium with system C, then systems A and C share a property called temperature.
- 1.4: The Perfect Gas
- One way to begin to describe the nature of matter is to make a simplified, idealized model. The perfect gas is one such idealized model. In a perfect gas (or ideal gas), there are no interactions among the particles, which themselves have no volume. In this section it will be shown how a sample of idealized gas particles trapped in a container can be described by the perfect gas law, using the four variables of pressure, temperature, the number of gas particles, and the volume of the container.
- 1.9: Functions of Two Independent Variables
- A function of two independent variables, z=f(x,y) , defines a surface in three-dimensional space. For a function of two or more variables, there are as many independent first derivatives as there are independent variables.
- 1.10: The Equation of State
- An equation of state is an expression relating the density of a fluid with its temperature and pressure. Note that the density is related to the number of moles and the volume, so it takes care of these two variables together. There is no single equation of state that predicts the behavior of all substances under all conditions.
- 1.11: Compressibility and Expansivity
- A very important property of a substance is how compressible it is. Gases are very compressible, so when subjected to high pressures, their volumes decrease significantly (think Boyle’s Law!) Solids and liquids however are not as compressible. However, they are not entirely uncompressible! High pressure will lead to a decrease in volume, even if it is only slight. And, of course, different substances are more compressible than others.