Yes, carbon dioxide is one molecule. A molecule is an arrangement of atoms, and carbon dioxide is one carbon atom with an oxygen atom bound to both sides.It can be represented this way: O=C=OOr this...
At normal temperature and pressure, carbon dioxide IS a gas. It doesn't normally react with most familiar gases, including "natural gas" or our atmosphere.
If you put a burning splint overtop of a test tube full of hydrogen, it will pop. If you put a burning splint in a test tube with carbon dioxide, it will be extinguished. Also, if you bubble carbon...