# What are the changes that occur inside a helium balloon as it rises from sea level?

Aug 28, 2017

We assume a constant temperature, and thus ${P}_{1} {V}_{1} = {P}_{2} {V}_{2}$. And since ${P}_{2} \text{<<} {P}_{1}$, ${V}_{2} \text{>>} {V}_{1}$ in order to compensate for the pressure drop. Since ${V}_{2}$ (and ${V}_{1}$) displaces a mass of air that is greater than the mass of the balloon, the balloon rises even higher in altitude.