Simple Answer:
Warm air rises during convection. Perhaps better said, natural convection of air is the rising of less-dense warm air relative to the more-dense cold air.
This is a simple matter of buoyancy. Gravity pulls everything downward, but the pull is proportional to mass and items immersed in a fluid that have lower mass per unit volume than the fluid will tend to float, i.e. experience a buoyant force up as gravity pulls harder downward on the surrounding fluid.
Causes and Explanation:
Everyone says "Warm air rises" and that is an example of natural convection. Convection requires a fluid, heat source and gravity. The heat source causes a temperature gradient in the fluid so that buoyancy of the warmer fluid causes it to rise.
Buoyancy is the reasons bubbles rise and hot air balloons float and anything light, like a piece of wood, raises to the surface. The gravitational force experienced by a volume of material is just its weight, i.e. mass times gravity. Mass is the density of the material times its volume. So, if the object (like wood) has a lower density than water, the force of gravity on the object is less than the equivalent volume of water. The buoyant (upward) force is the difference in the wight of the object and the weight of the same volume of liquid.
Light objects experience the upward buoyant force and if the fluid (air or water or any fluid) is heated and expands, then it has a larger volume and less density and it also experiences the upward force.
The natural buoyancy of warmer fluids causes the force that moves the fluid and that movement is what we call natural convection.
Other Aspects:
Trachea
Tidal volume refers to the amount of air that moves in or out of the lungs during normal breathing. It represents the volume of air inspired or expired with each breath.
The diaphragm contracts during inhalation, allowing the lungs to expand and fill with air. This helps to create negative pressure in the chest cavity, drawing air into the lungs. During exhalation, the diaphragm relaxes and moves back up, helping to push air out of the lungs.
The diaphragm primarily moves downward during inhalation, creating a vacuum that allows air to flow into the lungs. During exhalation, the diaphragm relaxes and moves upward, pushing air out of the lungs. This rhythmic contraction and relaxation facilitate the breathing process. Overall, the movement is a key component of respiration.
During inhalation, the diaphragm contracts and moves downwards, causing the chest cavity to expand and draw air into the lungs. During exhalation, the diaphragm relaxes and moves upwards, allowing the chest cavity to decrease in size and push air out of the lungs. These movements ensure proper ventilation of the lungs.
Warm air is displaced by cooler denser air
During convection, air moves due to temperature differences. Warmer air molecules expand and become less dense, causing them to rise. Cooler, denser air then moves in to replace the rising warm air, creating a convection current. This cycle of warm air rising and cool air sinking is how air moves during convection.
Movement of air (and water) is all to do with temperature. Warm air (and water) rises, while cold air (and water) sinks.
Trachea
Air moves into the lungs when the diaphragm is flattened. The diaphragm is relaxed (arched) during expiration.
the diaphragm
because the air warms as it moves down
When cool air moves from the oceans towards the beach during the day, it is known as a sea breeze. This happens because land heats up faster than water, causing the air above the land to rise. As the warm air rises, cooler air from the ocean moves in to replace it, creating the sea breeze effect.
prevent each alveolus from collapsing as air moves in and out during respiration
Your diaphragm moves downward during exhaling.
Heat moves through liquids by the gases moving towards the convention.
how does the air around us moves?