Substance Q could be oxygen ([tex]O_2[/tex])
Substance R could be carbon dioxide ([tex]CO_2[/tex])
What are molecules?
The smallest particle of a substance that has all of the physical and chemical properties of that substance.
There are 2 oxygen atoms in 1 molecule of oxygen. It is a di-atomic gas.
Carbon dioxide is a chemical compound composed two oxygen atoms covalently bonded to one carbon atom.
Hence, substance Q could be oxygen ([tex]O_2[/tex]). substance R could be carbon dioxide ([tex]CO_2[/tex])
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