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

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.

The fact that a balloon filled with air does not rise as a balloon filled with helium suggests that the density of helium is different from that of air.

To understand this better, let's take a look at the concept of density. Density is defined as the mass of a substance per unit volume. In simpler terms, it measures how much matter is packed into a given space. The formula for density is:

Density = Mass / Volume

Now, when it comes to the comparison between helium and air, we know that helium is a lighter gas than air. This means that for an equal volume of helium and an equal volume of air, the helium weighs less than the air. In other words, the mass of helium is lower while the volume remains the same.

Since the density is calculated by dividing the mass by the volume, if the mass (numerator) is lower than that of air while the volume (denominator) is the same, the density of helium would be less than the density of air. Therefore, the correct answer is:

B. Helium is less dense than air