Gas Laws

Similar to when I initiated reading about thermodynamics, I started my readings of the gas laws by not trying to connect the laws to the engine, but to try to fully understand the laws. The gas laws give the relationships between pressure, volume, temperature and the amount of a gas. The laws assume that the gas is an ideal gas. This means that the particles of the gas do not attract nor repel each other. This extends to mean that the particles will not react with one another. An ideal gas also assumes that the particles of the gas are of similar volume, which is inconsequential. This means that the volume of the particles gas is so small that the volume of the particles does not affect how the particles interact with its surroundings.

The gas laws consist of four laws which can be combined to form the ideal gas law. The first of these laws is Boyle’s law; the pressure-volume law. This law states that the volume of a given amount of gas held at a constant temperature varies inversely with the applied pressure. This means that a gas will have more pressure at a smaller volume and more volume at a smaller pressure. When graphed the law shows that V ∝ 1/p.

The second gas law is Charle’s law. This law gives the relationship between temperature and volume. Charle’s law states that the volume of a given amount of gas held at constant pressure is directly proportional to kelvin temperature (V ∝ T). Similarly, the third gas law, the Gay-Lussac’s law shows the relationship between temperature and volume. This law states that the pressure of a given amount of gas held at constant volume is directly proportional to the kelvin temperature (P ∝ T). 

The final law is Avogadro’s law, the volume-amount law. This law simply explains that when pressure and temperature are kept constant, the volume is directly proportional to the amount of particles (V ∝ n). In other words, more particles require more space. 

These four laws can be used to create the ideal gas law, which is used to analyze a gases pressure, volume, temperature and amount. By combining the proportionality statements of Charle’s law and Avogadro’s law the following proportionality statement is created: V ∝ nT. Furthermore by combining this statement with Boyle’s law the proportionality statement now appears as, V ∝ nT/P. or PV ∝ nT. The equation of this statement looks as follows, PV = nRT. This is known as the ideal gas law. 

Similar to studying thermodynamics, these laws were simple to understand when not trying to apply them to the Stirling Engine. As a result, I needed no clarification on my readings and further research was not required. This is partly because the textbooks I was reading did not offer much information on the gas laws, so the majority of my readings were completed online.

Sources: 

Serway, R. (1982). Physics: For scientists and Engineers. New York, NY: CBS College Publishing

Gas Lays. (n.d.) Gas Laws. Retrieved June 9, 2014 from “chemistry.bd.psu”: chemistry.bd.psu.edu/jircitan/gases.html

Goldberg, T. (n.d.) Ideal gas equation: PV = nRT, Retrieved June 9, 2014 from “KhanAcademy”: www.khanacademy.org/science