It keeps it up
Hydrogen is used. Sorry. Just regular air is used in a hot air balloon, it is heated which makes it lighter and less dense and therefore provide lift. Hence the name hot air balloon. Hydrogen is used in a gas balloon.
Anything less dense than air (hydrogen, helium, hot air).
A hydrogen balloon rises in air because the hydrogen gas inside the balloon is lighter than the surrounding air. This makes it buoyant, causing it to float upwards. The difference in density between the hydrogen gas and the air creates an upward force, lifting the balloon off the ground.
A hot air balloon doesn't contain helium or hydrogen.
A hydrogen balloon in air will rise due to the fact that hydrogen gas is less dense than air. The balloon will continue to rise until it reaches an altitude where the density of the surrounding air matches its own density. If ignited, the hydrogen in the balloon can react with oxygen in the air and create a fire or explosion.
Hydrogen is not used to inflate hot air balloons. Just regular air is used which is then heated to make the balloon more buoyant as hot air weighs less than cold air. Hence the name hot air balloons.
Hydrogen is less dense than air, so it creates a buoyant force that causes the balloon to rise. This is because the density of the hydrogen inside the balloon is lower than the surrounding air, making it lighter and causing it to float upwards.
A balloon filled with hydrogen gas floats in air because hydrogen is lighter than air. The buoyant force acting on the balloon is greater than the gravitational force pulling it down, allowing it to float.
hydrogen
If the balloon were lofted by hydrogen, it would not be a "hot air" balloon, as no heat would be needed. Indeed, to get even a spark near the hydrogen would be for the balloon to go up in a huge fireball. Hydrogen was abandoned as a lift gas for lighter -than-air craft in the 1930's, exactly for that reason.
'Hot air' balloons don't use hydrogen. They use hot air. Balloons that use hydrogen are not referred to as 'hot air' balloons. The only balloons that can accurately be referred to as 'hot air' balloons are the members of the balloon population that derive their lift/buoyancy from the presence of hot air. Of course, if a balloon used no hot air, then it could freely be referred to as a 'hydrogen' balloon, a 'helium' balloon, a 'water' balloon, etc., depending in congruent harmony with the nature of whatever substance had been chosen with which to inflate it it in order to maintain its fulsome shape.
Hydrogen gas was used in air balloons because it is much less dense than air and therefore rises, taking the balloon with it. it is unfortunately also very explosive so not used often anymore.