I tried a lot, and I don't get the answer. Please help! Thank you in advance.

Indicate true or false whether the following statements are a consequence of the second law of thermodynamics.
1. No device can transform a given amount of heat completely into work.
2. It is so improbable for the entropy of an isolated system to decrease that it never happens.
3. Time appears to have a direction.
4. Natural process tend to move toward a state of greater disorder.

The second law is all about entropy. Tell us what you think the answers are to these 4 question, and why, and we'll review your attempt.

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Originally Posted by ebaines

The second law is all about entropy. Tell us what you think the answers are to these 4 question, and why, and we'll review your attempt.

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My answer as follow:
1. True, because depends on the second law it is impossible to transfer the complete heat to work.
2. I guess is false, I am not sure about this. But I know the entropy is always larger than 0.
3. I guess is false, I didn't find any statement that say in the second law the time has direction.
4. I guess is false.

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Originally Posted by yhzhang

My answer as follow:
1. True, because depends on the second law it is impossible to transfer the complete heat to work.

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Right!

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Originally Posted by yhzhang

2. I guess is false, I am not sure about this. but i know the entropy is always larger than 0.

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The wording of this one is a bit confusing. For a closed system entropy must increase. So the phrase that "it is so improbable [to decrease] that it never happens" is true.

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Originally Posted by yhzhang

3. I guess is false, I didn't find any statement that say in the second law the time has direction.

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This seems a bit off topic, but some have argued that since entopy for a closed system must always increase, it defines an "arrow of time" that makes it impossible for events to happen backwards. The classic example is watching a movie of an explosion, or a glass shattereing - if you run the movie backwards it seems obviously unnatural, because as the bomb or the shattered glass reassembles itself it's entropy appears to decrease, and we easily recognize that as unnatural. This is as contrasted to other other physical phenomenon that occur in classical physics - for example if I show a movie of a ball arcing through the air it's almost impossible to tell whether the movie is the original or a version running backwards.

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Originally Posted by yhzhang

4. I guess is false.

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No, it's true. Natural processes tend to a higher state of disorder unless energy is added in. So for example if a building is left unattended for a few hundred years over the years it becomes a shambles, overgrown with weeds, windows broken, roof blown away, etc. All that decay is a form of disorder - hence the entropy of the building increases.