Why does a balloon filled with helium rise while a balloon filled with an equal volume of average atmospheric air does not?

Question

A.
Helium has no mass, but air does.
B.
Helium has a lower density than air.
C.
Helium increases the balloon's mass more than air.
D.
Helium has a higher density than air.

Answer 1

The correct answer is:

B. Helium has a lower density than air.

A helium-filled balloon rises because the density of helium is less than the density of the surrounding air. This difference in density creates an upward buoyant force on the balloon, allowing it to rise.