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Balloons are a great demonstration of the relationship between pressure, volume and temperature. The average kinetic energy generated by the particles collding inside the balloon create a pressure. If a balloon is brought out into the cold, it will shrivel as the collisions between the particles become fewer. The relationship between the these theree aspects can be summed in the Ideal Gas Law, PV = nRT. This law assumes that all the particles are acting independently, or in other words that they are not being attracted to one another. This is a fair assumption the further from the phase boundries the gas is.
As the equation shows, pressure and volume have an inverse relationship to temperature. Temperature is always in units of Kelvin. Pressure can be in Kpa or pascals. Volume is in meters cubed. N is the number of moles. R is the Rydenberg constant and will depend on what units the other variables are in.
Pv = nRT is a simplified model. When graphed out, the area under the points is the work done. In order to get heat and work, both tied to the temperature, it is important to use the First Law of Thermodynamics: delta U= Q + W. delta U is the internal energy, Q is heat transferred to the system, and W is work done on the system. In my working models, I am not as focused on this formula.
Work done on a system. http://www.ahsd.org
There are four main processes the Ideal Gas Law is used for: isobaric, isochoric, isothermic, and adiabadic.