Final answer:
Each breath results in moisture condensing and heat being lost due to the breathing process and the nature of compressed air. During respiration, the exchange of warm, humidified air with colder external air causes visible condensation, known as seeing your breath. Increased depth of breathing can lead to additional heat loss from the lungs.
Step-by-step explanation:
Due to the nature of compressed air, each breath results in moisture condensing & heat being lost. When air is compressed, as in a canister, releasing it causes a drop in temperature as the gas molecules spread out, absorbing energy from their surroundings. The same principles apply to the warm, humidified air exhaled from our lungs. The water vapor in your exhaled breath cools suddenly when it reaches the colder outside air, causing the vapor to condense into a fog of tiny droplets, which is why you can 'see your breath' on a cold day.
Intake of air through the nasal cavity helps to warm the air to body temperature and humidify it, protecting the body from cold and dry air. During breathing, the depth increases, and the person may breathe through an open mouth, leading to even more heat loss from the lungs. The gas exchange during respiration additionally plays a role, as oxygen is extracted from and carbon dioxide is added to alveolar air, contributing to changes in partial pressures and the overall composition of alveolar air.