Why does water freezing not violate the second law of thermodynamics? (Hint: Think in terms of a system)
The entropy of the water decreases when it freezes and goes into a more ordered crystaline state. However, heat is released to the environment in the process. If the surrounding envrinment is also at 0 C (273 K), the heat gained by the environment equals the heat lost by the ice, so there is no net change in system entropy. If the environment is colder than 0 C while the ice freezes, the environment gains more entropy that the ice loses, because
Q/273 < Q/Tenvironment. Net system entropy increases, which is consistent with the second law.
To understand why water freezing does not violate the second law of thermodynamics, we need to consider the concept of a system. In thermodynamics, a system refers to a specific portion of matter or space that we wish to study and analyze.
When water freezes, it undergoes a phase transition from a liquid state to a solid state. During this process, the entropy of the water decreases as it becomes more ordered and takes on a crystalline structure. This might seem contradictory to the second law of thermodynamics, which states that the entropy of an isolated system tends to increase over time.
However, it is important to consider the system as a whole, including not only the water but also the surrounding environment. When water freezes, heat is released to the environment. If the surrounding environment is at the same temperature as the freezing point of water (0 degrees Celsius or 273 Kelvin), the heat gained by the environment is equal to the heat lost by the ice.
In this case, the entropy gained by the surrounding environment due to the heat it receives is the same as the entropy lost by the ice as it becomes more ordered. As a result, there is no net change in the entropy of the system consisting of the water and the environment. Thus, the entropy of the overall system remains constant, preserving the second law of thermodynamics.
It is worth noting that if the environment is colder than 0 degrees Celsius while the ice freezes, the environment gains more entropy than the ice loses. The heat transfer between the ice and the colder environment will result in a decrease in entropy for the ice and an increase in entropy for the environment. In this case, the overall system entropy increases, which is consistent with the second law of thermodynamics.