Question

A balloon filled with helium floats in the air. What does this tell you about the density of helium?

Answer 1

For air, which has a molar mass of 29.0 g/mol, this gives a density of 1.18 g/l. Helium, which has a mass of 4.00 g/mol, has a density of 0.164 g/l.

Answer 2

helium is denser than air