In this chemistry lesson, students learn about the fractional distillation of liquid air and how to conduct experiments to identify the presence of different gases in the atmosphere. The instructor explains that air predominantly consists of nitrogen (78%) and oxygen (21%), with the remaining 1% made up of noble gases like argon, neon, helium, krypton, and xenon, as well as carbon dioxide. A detailed experiment is described where copper wire reacts with oxygen to form copper oxide, demonstrated using a closed apparatus with syringes to measure changes in air volume and confirm the oxygen percentage.