Question

A balloon filled with air does not rise as a balloon filled with helium. What does this tell you about the density of helium?

A. Helium is more dense than air
B. Helium is less dense than air
C. The two gases have the same density
D. When heated, helium becomes more dense

Answer 1

Less dense objects float on more dense objects. For example, a piece of wood floats on water because the water is more dense than wood. Likewise, a balloon filled with He will float in air because air is more dense than He.