If melting of ice into water increases entropy, then does its freezing due to naturally occurring cold temperatures decrease the entropy? And does the entropy of the ice decrease or that of the whole Universe too? If it does not in case of the Universe, then why?
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The second law of thermodynamics states that the entropy of an isolated system never decreases.
If you put water in a container in deep space it will cool down and freeze. The entropy of the container and water will decrease.
The reason the container of water does not break the second law is that it is not an isolated system. In an isolated system, there is no exchange of energy and matter with anything else. The container does lose energy that is radiated out as infrared light so not an isolated system. You can approximate the container and what is radiated out as a isolated system,
So the question is what is the change in entropy of the container and what is radiating out into space? The answer, in this case, will be that it has not decreased, it will in fact increase.
If you put water in a cold enviorment it gets cooled down by heating out the sounding area. The temperature will equalize, The entropy when the temperature equalized is higher than when the water was warmer and surrounding was cooler.
So entropy can and do locally decrease but at the same time, it will increase more in the surrounding that it thermodynamically interact with. A local decrease it not against the law of thermodynamics.
Water freezes by releasing heat to the outside world. The single block of ice becomes colder by heating the outside universe a bit. The universe outside of the block of ice gains more entropy than what’s lost by the block of ice so, overall, the entropy increases in the whole universe.
This is hard to translate to Eli5 because it involves some concepts of thermodynamics so this is going to be long. Tldr at the bottom.
First of all, entropy is a measure of how disordered or random a system is. The more possible ways a system can be arranged, the higher its entropy. For example, a gas has higher entropy than a liquid, because the gas molecules can move around more freely and occupy more space.
Melting of ice into water increases entropy, because the water molecules have more freedom to move than the ice molecules.
The water molecules can slide past each other and take different shapes, while the ice molecules are fixed in a rigid structure.
Therefore, melting of ice is a process that increases the disorder or randomness of the system.
However, entropy is not only a property of the system, but also of the surroundings.
The surroundings are everything outside the system that can exchange energy or matter with it.
For example, if you have a glass of ice water on a table, the system is the ice water and the surroundings are the table, the air, and everything else in the room.
When ice melts into water, it absorbs heat from the surroundings. This means that the surroundings lose some energy and become colder.
The loss of heat from the surroundings also means that they lose some entropy, because heat is a form of disorder or randomness.
Therefore, melting of ice is a process that decreases the entropy of the surroundings.
The second law of thermodynamics states that the total entropy of the system and the surroundings must always increase or stay the same for any spontaneous process.
A spontaneous process is one that happens naturally without any external force or intervention.
For example, ice melting into water at room temperature is a spontaneous process, because it happens by itself without any external heating or cooling.
So how can ice melting into water be spontaneous if it decreases the entropy of the surroundings? The answer is that it increases the entropy of the system (the ice water) more than it decreases the entropy of the surroundings.
The net result is that the total entropy of the system and the surroundings increases, which satisfies the second law of thermodynamics.
Now let’s consider the reverse process: freezing of water into ice.
This process decreases the entropy of the system (the ice water), because it makes the water molecules more ordered and less free to move. However, it also increases the entropy of the surroundings, because it releases heat to them. The heat makes the surroundings warmer and more disordered.
Freezing of water into ice can be spontaneous if it happens at low enough temperatures, such as in a freezer or outside in winter.
At these temperatures, the increase in entropy of the surroundings due to heat release is greater than the decrease in entropy of the system due to freezing.
The net result is that the total entropy of the system and the surroundings increases, which satisfies the second law of thermodynamics.
However, freezing of water into ice cannot be spontaneous at higher temperatures, such as at room temperature or above.
At these temperatures, the increase in entropy of the surroundings due to heat release is smaller than the decrease in entropy of the system due to freezing.
The net result is that the total entropy of the system and the surroundings decreases, which violates the second law of thermodynamics.
Tldr:
* Entropy is a measure of disorder or randomness.
* Melting of ice into water increases entropy of the system (the ice water) and decreases entropy of the surroundings (everything else).
* Freezing of water into ice decreases entropy of the system (the ice water) and increases entropy of the surroundings (everything else).
* The second law of thermodynamics states that the total entropy of the system and the surroundings must always increase or stay the same for any spontaneous process.
* Melting of ice into water is spontaneous at high temperatures, because it increases the total entropy of the system and the surroundings.
When water freezes into ice, it actually increases the entropy of the universe.this might seem strange, but let me explain. Entropy is a measure of how much disorder or randomness there is in a system. When water freezes, it becomes more ordered and structured, which might make you think that it’s decreasing entropy. However, the process of freezing actually releases heat into the environment, which increases the overall entropy of the universe. So even though the ice itself might be more ordered, the universe as a whole becomes more disordered. It’s like cleaning up your room – even though your room becomes more ordered, the rest of the house might become more disordered because you moved things around.
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