Here's why:

* Hydrogen is a specific chemical element, represented by the symbol "H". It's the lightest element in the periodic table and is very abundant in the universe.

* Gas is a state of matter. A gas has no fixed shape or volume and its particles are far apart.

Think of it this way:

* Hydrogen is like the ingredient, "flour."

* Gas is like the state of the ingredient, like "flour in a bag" (solid), "flour in a bowl" (liquid), or "flour in the air" (gas).

So, while hydrogen can exist as a gas, it's not the same thing as "gas" in general. There are many other gases, like oxygen (O2), nitrogen (N2), carbon dioxide (CO2), and even helium (He), just to name a few.