When a mixture of nitrogen (N2) and oxygen (O2) is separated into two pure samples, one containing only N2 and the other only O2, the entropy of the system changes significantly.
Initially, the mixture has a certain level of entropy due to the randomness and disorder associated with the mixed gases. Entropy, in a general sense, is a measure of the disorder or the number of ways a system can be arranged. In a mixed gas, the molecules of N2 and O2 are intermixed, allowing for a high degree of freedom in their arrangement.
When the gases are separated, each gas is now in a more ordered state. The pure N2 sample consists solely of nitrogen molecules, while the pure O2 sample consists solely of oxygen molecules. This separation reduces the randomness of the system overall, as there are fewer configurations available now that the gases are isolated from each other.
Thus, the entropy of the system decreases when the mixture is separated into two pure components. The initial mixed state has a higher entropy than the final state of separated gases due to the increased order. In summary, during the separation of the N2 and O2, the overall entropy of the system decreases because the disorder is reduced by isolating the gases.