(a) Consider sliding a glass across a wooden counter by giving it a light push.
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Question
(a) Consider sliding a glass across a wooden counter by giving it a light push. It will come to rest after a while. Is this process reversible or irreversible? Think about this process if we play it backwards in time. Describe what happens. Discuss what is going on on the microscopic scale of the molecules of the glass and counter. (3 points) (b) Now think about a glass of water. Suppose we put a drop of red syrup into the water. Describe what happens. Is this a reversible or an irreversible process? Once again, think about running the movie of this process backwards in time. Discuss what is going on on the level of the molecules of water and syrup. (3 points) (c) Describe a reversible process. What must be true about the entropy during such a process? (3 pointsExplanation / Answer
(a) The process is irreversible as it changes the surrounding by providing the heat which dissipated due to the friction. Even if the process is reversed, the heat given to the surrounding will not be taken back by the process. Although we achieve the initial state but the surrounding will not remain same hence the process is irreversible.
(b) This process is also irreversible. As we drop the syrup, it will get completely dissolve and its almost impossible to get it back by any process which does not affect the surrounding.
(c) The process in which the system and surroundings can be restored to the initial state from the final state without producing any changes in the thermodynamic properties of the universe is called a reversible process. For a reversible process, the entropy is a constant and net change in entropy is always zero.
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