Why do hot air balloons rise through convection?

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

Convection is a process by which heat is transferred through a gas or liquid by the bulk movement of heated particles to cooler areas. In the case of a hot air balloon, the air inside the balloon is heated by a burner, which causes the air molecules to move faster and spread out. This makes the air inside the balloon less dense, or lighter, than the cooler air outside the balloon.

The principle of buoyancy then comes into play. This principle states that an object will float in a fluid if it is less dense than that fluid. Since the hot air inside the balloon is less dense than the cooler air outside, the balloon will rise. This is similar to how a cork, which is less dense than water, will float if you put it in a bucket of water.

The balloon will continue to rise until the air inside cools down and becomes denser, or until it reaches an altitude where the air outside is as hot and therefore as dense as the air inside the balloon. To make the balloon rise higher, the pilot can turn on the burner to heat the air inside the balloon and make it less dense. To make the balloon descend, the pilot can let the air inside the balloon cool down, or let some hot air out of the balloon to make it denser.

In summary, the rise and fall of hot air balloons is a wonderful demonstration of the principles of convection and buoyancy. The hot, less dense air inside the balloon rises through the cooler, denser air outside, and the balloon goes along for the ride.