Answer: The gas law which applies here is :Charle's Law
Explanation:
The main principle behind this is that, warm air rises in the cooler air.Which implies that hot air is less denser than the cooler air. Due to this property hot air rises up in the sky.
Density decrease with increase in volume due to this hot air balloon rises up in the air
Also the volume occupied by the gas increase with increase in temperature at constant pressure known as Charle's law.
So, during preflight the propane torch is lit to warm up the air present inside the balloon.
Propane torch is lit inside a hot air balloon during pre-flight preparation because the heat from the touch is needed to heat the cold air inside the balloon, so that the air will expand and become less dense and rise, thus providing a lift for the balloon. This is line with charle's law, which states that, the volume of a fixed mass of ideal gas is directly proportional to the absolute temperature. This law implies that, as the temperature of the air inside the balloon increase, the volume of the balloon also increases.
