Why do hot air balloons rise?

Hot air balloons rise because the hot air inside the balloon is less dense than the cooler air outside.

Hot air balloons operate based on a very basic scientific principle: warmer air rises in cooler air. Essentially, hot air is lighter than cool air, because it has less mass per unit of volume. This is known as the principle of buoyancy. When the air inside the balloon is heated, it becomes lighter than the cooler air outside. This causes the balloon to float upwards.

The process begins with the balloon being filled with cold air, which is then heated. The heat source, usually a burner, is located at the mouth of the balloon. As the air inside the balloon heats up, it expands and becomes less dense. This decrease in density compared to the cooler, denser air outside the balloon causes the balloon to rise.

The pilot can control the altitude of the balloon by manipulating the temperature of the air inside the balloon. To ascend, the pilot heats the air, and to descend, the pilot allows the air to cool. This is achieved by either turning the burner on or off, or by releasing hot air through a vent at the top of the balloon.

In summary, the principle of buoyancy, which states that less dense materials will rise in more dense materials, is the key to understanding how hot air balloons work. The hot, less dense air inside the balloon rises in the cooler, denser air outside, causing the balloon to ascend. The pilot can control the balloon's altitude by adjusting the temperature of the air inside the balloon.