Final answer:
Nitrogen and oxygen can be separated from air by taking advantage of their different boiling points through fractional distillation. Nitrogen, which is abundant in the atmosphere, is isolated due to its lower boiling point. In contrast, oxygen is separated as the liquid air mixture warms up, due to its higher boiling point.
Step-by-step explanation:
To obtain samples of nitrogen and oxygen from air, specific methods based on their physical properties are used. For nitrogen, fractional distillation of liquid air is employed because it makes up approximately 78% of the Earth's atmosphere. During this process, liquid air is separated into its components based on the different boiling points. Nitrogen can be collected due to having a lower boiling point than oxygen.
On the other hand, commercial oxygen production also starts with the cooling and compressing of air to create liquid air. As the liquid air warms, oxygen, which has a higher boiling point than nitrogen, can be separated from the mixture. This method takes advantage of the 90 K boiling point of oxygen, compared to nitrogen's 77 K.
While obtaining pure nitrogen and oxygen can be done on a large scale as described, it's worth noting that humans obtain these elements differently. We assimilate oxygen through the air we breathe and the water we drink. In contrast, we get nitrogen in the form of proteins from the food we consume, not directly from the air.