Answer:
Oxgen- cannot be separated
Water - chemical change
Gold - cannot be separated
Carbon Dioxide - chemical change
Carbon - cannot be separated
Step-by-step explanation:
A pure substance, which can either be an element or a compound, contains only one type of such element or compound. In opposition to a mixture, pure substances cannot be separated by physical means.
- Elements as a pure substance cannot be separated because it contains only one type of atom. However, compounds contain two or more types of atoms, and hence, can only be separated into its individual atoms via chemical means.
In this question, oxygen (O2), Gold (Au) and carbon (C) are all elements and hence cannot be separated. Carbon dioxide (CO2) and water (H2O) are compounds because they contain two different atoms respectively, hence, can be separated into individual atoms.