Oxygen gas is not heavier than air. In fact, it's slightly lighter than air. Here's why:

* Air composition: Air is a mixture of gases, primarily nitrogen (78%) and oxygen (21%).

* Molar mass: Oxygen gas (O2) has a molar mass of 32 g/mol. Nitrogen gas (N2) has a molar mass of 28 g/mol.

* Density: Since oxygen is a smaller component of air and has a slightly higher molar mass than nitrogen, air is denser than pure oxygen.

Therefore, oxygen gas is slightly lighter than air.

However, it's important to note that:

* Oxygen is heavier than some other gases, like helium.

* The difference in weight between oxygen and air is very small.

* The "heaviness" of a gas can be influenced by factors like temperature and pressure.

Let me know if you have any other questions!