|Can you tell me the difference in lifting power of helium versus hydrogen? — FL, Napa, CA
A balloon experiences an upward buoyant force that's equal in amount to the weight of the air it displaces. If that balloon is filled with helium or hydrogen, both of which have very low densities, then this upward buoyant force may be more than the balloon's weight and the balloon may accelerate upward. Helium weighs a little more per cubic foot or cubic meter than hydrogen does, so replacing the helium with hydrogen will make it easier to float the balloon. A cubic foot of hydrogen weighs 0.0056 pounds less than a cubic foot of helium and a cubic meter of hydrogen weighs 89 grams less than a cubic meter of helium. Any weight saving made by replacing helium with hydrogen in your balloon can be viewed as extra lifting power. As you can see, the effect is small and hydrogen is a whole lot more dangerous than helium.