Final answer:
Tea bags fly after they burn out due to changes in air pressure and temperature, not because of magnetic forces, chemical reactions, or any anti-gravity effect. The hot air produced has lower density and is lifted by buoyant force.
Step-by-step explanation:
The phenomenon of tea bags flying after they are burned out is due to air pressure changes. Once a tea bag is lit, it results in a flame that produces hot gas. This hot gas is still at atmospheric pressure, as it is in mechanical equilibrium with the air around it. However, as per the ideal gas law, the number density (N/V) of this hot gas, due to its higher temperature, is less than that of the surrounding air.
Therefore, the hot air has a lower density and is lifted by the buoyant force, causing the burned out tea bag to rise or 'fly'. This phenomenon is not due to any chemical reaction within the tea bag itself or any magnetic forces, nor is it related to any anti-gravity effect. It's a simple demonstration of how changes in air pressure and temperature can lead to changes in density, and consequently, buoyancy.
Learn more about air pressure changes