Final answer:
Carbon dioxide is a pure substance with carbon and oxygen chemically bonded in a fixed proportion, and this composition is consistent across different samples of the gas.
Step-by-step explanation:
The gas carbon dioxide is a pure substance, and it is true that carbon and oxygen are chemically bonded in it. This means that carbon and oxygen do not retain their original identity within the compound, as they are joined to form carbon dioxide molecules through chemical bonds. Specifically, there is one carbon atom and two oxygen atoms connected by two double covalent bonds in each molecule of carbon dioxide. As a compound, the proportion of carbon to oxygen remains constant and doesn't vary among different samples of this gas. Therefore, it cannot be separated into its component elements using physical methods; chemical processes are required to break the bonds between carbon and oxygen atoms.