Here's why:

* Helium is a noble gas, meaning it's a single element. It's lighter than air and does not burn.

* Hot air is regular air (a mixture of gases like nitrogen, oxygen, and others) that has been heated.

While both helium and hot air are used to make things float (like balloons), they achieve this in different ways:

* Helium: Helium is lighter than air, so it creates buoyancy. It's used in balloons for this reason.

* Hot air: Hot air is less dense than cold air. This means it has less mass per unit volume, making it rise. This is why hot air balloons work.

So, while both helium and hot air can lift objects, they do so through different physical principles. They are not the same gas.