Entropy Variation - System, Neighborhood and Universe

In summary, entropy is a measure of disorder in a system and tends to increase over time in a closed system. In an open system, it can decrease as energy and matter flow through it. In the neighborhood of a system, entropy can increase or decrease depending on interactions with its surroundings. The second law of thermodynamics states that the entropy of the universe can never decrease. Entropy variation can affect the behavior of a system, such as decreasing efficiency in a closed system or allowing for the formation of ordered structures in an open system. While it is possible to reverse entropy in theory, it is highly unlikely to occur spontaneously in a closed system and most cases lead to an increase in entropy and disorder.
  • #1
jaumzaum
434
33
I learned ΔSuniv = ΔSsys + ΔSneib

If ΔSuniv > 0 the process is spontaneous.

But ΔS = Q/T right? Shouldn't Qsys = -Qneib? (The heat released by the system = - heat released by the neighborhood)
I cannot understand why this is wrong!

If it were the case, ΔSuniv would be always zero

Can anyone help me?

[]`s
John
 
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  • #2
##\Delta S=Q/T## only for reversible processes.For irreversible processes, ##\Delta S>Q/T##.
 

1. What is entropy and how does it vary in a system?

Entropy is a measure of the disorder or randomness in a system. It is a thermodynamic quantity that increases with an increase in disorder. In a closed system, entropy tends to increase over time, meaning that the system becomes more disordered. However, in an open system, there can be a decrease in entropy as energy and matter flow through it, allowing for the creation of ordered structures.

2. How does entropy vary in the neighborhood of a system?

In the neighborhood of a system, entropy can either increase or decrease depending on the interactions between the system and its surroundings. If the system releases energy or matter into its surroundings, the entropy of the neighborhood increases. On the other hand, if the system takes in energy or matter from its surroundings, the entropy of the neighborhood decreases.

3. Can the entropy of the universe ever decrease?

No, the second law of thermodynamics states that the total entropy of the universe can never decrease, only increase or remain constant. This means that as a whole, the universe is constantly moving towards a state of maximum disorder.

4. How does entropy variation affect the behavior of a system?

The increase or decrease of entropy in a system can affect its behavior in various ways. For example, in a closed system, an increase in entropy may result in a decrease in the efficiency of energy conversion. In an open system, a decrease in entropy may allow for the formation of more complex and ordered structures. Overall, entropy variation plays a crucial role in determining the direction and efficiency of energy and matter flow in a system.

5. Can entropy be reversed in a system?

In theory, it is possible to reverse the entropy of a system by removing disorder and creating a more ordered state. However, this would require an input of energy and is highly unlikely to occur spontaneously in a closed system. In most cases, entropy increases and is irreversible, leading to the natural tendency towards disorder in the universe.

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