This is a model of the Stirling Engine that Prof. Mason demonstrated for us. He put the thing on top of a beaker with really hot water and ice on top of the engine. What he said was that the difference in temperature makes the water flow rapidly. The lower part of the engine is a cylinder full of a liquid and a movable platform that spins the spinner as it moves up and down. The movement of water from the bottom of platform to the top where it gets cooled down and back down makes the platform move up and down and spin the spinner.
Prof. Mason explained that there are four thermodynamic processes through which the liquid inside the engine goes through in order to work. These are two isothermal processes and two isoentropic processes. But what are isoentropic processes?
They are processes where the entropy of the system doesn't change. In other words, the overall order of the molecules doesn't change. Officially, they are defined as Q/T (left side of the above picture) and they have units of J/K. On the the right of the above picture there are a few examples of events that do change entropy.
Another example of changing entropy is diffusion such as the diffusion of some green liquid into a beaker full of water.
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