So basically i am asking is entropy conserved?

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In summary, during a review for the AP Chemistry test, a question was posed about the change in entropy and energy when an ice cube is placed in hot water and sealed. The correct answer is that the energy remains constant while the entropy increases. Entropy is not conserved and the second law of thermodynamics states that it always increases in a closed system. Although total entropy cannot be measured, the change in entropy can be calculated. In this situation, the ice gains entropy while the water loses an equal amount. It is important to focus on changes in entropy between states of matter for the test.
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iluvsr20s
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The other day in class we were reviewing for the AP Chem test and came across a question regarding Entropy, the question was

If you put an ice cube in a container of hot water and sealed it completely, how would the entropy and energy values change?

I answered that Energy and Entropy would remain constant because all the energy from the water would go to the ice and all the entropy lost by the water would go to the ice.
The correct answer was that the energy would remain constant and the entropy would increase.

So basically i am asking is entropy conserved?
 
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iluvsr20s said:
So basically i am asking is entropy conserved?
No, entropy is not conserved. In general, for a closed system, such as the sealed container in your example, the total entropy cannot decrease but can only increase (or stay the same). In this particular example, the thermal energy redistributes to maximize entropy. Once thermal equilibrium is reached, the entropy will remain constant.
 
  • #3
To continue:

there is no "conservation of entropy" law. In fact, there is the second law of thermodynamics which says, specifically, that entropy always increases.

WE can't measure total entropy, but we can measure the change in entropy: In your hot water/ice situation, the ice is at 273 K and the water is at, let's say 350 K. THe change in entropy of the ice is found by dividing the heat that goes into it, over the temperature of the ice (+Q/T_cold). This produces an increase in entropy of the ice.

Of couse the heat that goes into the ice comes out of the water. Let's say that there is enough water at 350 K so that the temperature stays constant. The reduction of entropy in the water = the heat that leaves the water over the temperature of the water (-Q/T_hot). Q is the same for the water and the ice, but since T_hot is greater than T_cold, the increase in entropy of the water is more than the decrease in entropy of the water.
 
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Thanks it makes sense now. My teacher told me to just think of entropy changes from gas to liquid to solid for the chemistry test
 
  • #5
Just stick with the states of matter dealing with entropy at the AP chem level.
 

Related to So basically i am asking is entropy conserved?

1. What is entropy?

Entropy is a measure of the disorder or randomness in a system. It is a thermodynamic property that describes the amount of energy that is unavailable for work in a thermodynamic process.

2. Is entropy conserved?

No, entropy is not conserved. According to the second law of thermodynamics, the total entropy of a closed system will always increase over time, meaning that the disorder or randomness in the system will also increase.

3. How is entropy related to energy?

Entropy and energy are closely related. As the energy in a system increases, the entropy also increases, leading to a more disordered state. This is why the second law of thermodynamics states that energy will tend to spread out and become more disordered over time.

4. Can entropy be reversed?

In most cases, entropy cannot be reversed. The second law of thermodynamics states that the total entropy of a closed system will increase over time, but there are some exceptions. For example, in a biological system, living organisms are able to maintain a low entropy state by constantly taking in energy and expelling waste.

5. How does entropy affect the universe?

Entropy is a fundamental concept in thermodynamics and plays a crucial role in the functioning of the universe. It explains why energy tends to spread out and become more disordered over time, leading to processes such as heat transfer, chemical reactions, and the expansion of the universe. The increasing entropy of the universe is also believed to be the reason behind the irreversible nature of time.

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