Oxygen is a pure substance because it consists of only one type of atom, which is oxygen itself. It cannot be broken down into any simpler substances, and it has consistent properties that are characteristic of oxygen. 1
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Key Takeaways: Why is Oxygen a Pure Substance?
- Oxygen is a pure substance because it is composed of only one type of atom, specifically oxygen atoms.
- Pure substances have a constant chemical composition and cannot be separated into simpler substances by physical means.
- Oxygen is an element with the atomic number 8 and exists as a diatomic molecule (O2) in its elemental form.
- It is not a mixture because it does not contain different substances and meets the criteria of a pure substance.
Explanation: Why is oxygen a pure substance?
Oxygen is considered a pure substance because it is composed of only one type of atom, specifically oxygen atoms. A pure substance is a type of matter that has a constant chemical composition and cannot be separated into simpler substances by physical means, such as filtration, distillation, or evaporation. 2
Oxygen is an element with the atomic number 8 and is a member of the chalcogen group on the periodic table. 3
It exists in its elemental form as a diatomic molecule, which means that two oxygen atoms are chemically bonded together to form O2. 4
This molecular form of oxygen is the most stable and abundant form found in the Earth’s atmosphere, making up about 21% of the air we breathe. 5
Because oxygen is made up of only one type of atom, it is considered a pure substance and can be represented by a chemical symbol (O) on the periodic table.
Pure substances can exist in different states (solid, liquid, gas), and the state of oxygen depends on factors such as temperature and pressure.
Why is oxygen not a mixture?
Oxygen is not a mixture because it consists of only one type of atom, specifically oxygen atoms. A mixture, on the other hand, is a combination of two or more different substances that are not chemically bonded together and can be separated by physical means. 6
In the case of oxygen, it exists in its elemental form as O2, where two oxygen atoms are chemically bonded together. This molecular form of oxygen is consistent throughout the substance, and there are no other types of atoms or molecules present.
Therefore, it does not meet the criteria of a mixture, which requires the presence of at least two different substances.
Mixtures, such as air, contain various gases like nitrogen, oxygen, carbon dioxide, and others, which are not chemically bonded to each other. 7 These gases can be separated by physical methods, such as fractional distillation, due to their different boiling points.
However, when it comes to oxygen itself, it is not a mixture but a pure substance since it consists of identical oxygen atoms bonded together.
Oxygen is a pure substance, but is it an element or a compound?
Oxygen is an element, not a compound. An element is a pure substance made up of only one type of atom, and oxygen consists of only oxygen atoms (with the chemical symbol O).
It is one of the fundamental building blocks of matter and is found in the periodic table of elements.
Compounds, on the other hand, are substances formed when atoms of different elements chemically combine in fixed ratios. 8
Examples of compounds that contain oxygen include water (H2O), carbon dioxide (CO2), and ozone (O3).
Further reading
Why is Water a Pure Substance?
Why is Iron a Pure Substance?
Why is Copper a Pure Substance?
Is Brass a Pure Substance?
Why is Ice a Pure Substance?
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References
- Oxygen – Element information, properties and uses | Periodic Table. (n.d.). Oxygen – Element Information, Properties and Uses | Periodic Table. https://www.rsc.org/periodic-table/element/8/oxygen
- McCord, P. (n.d.). Matter – Breakdown. Matter – Breakdown. https://mccord.cm.utexas.edu/chembook/page-nonav.php?chnum=1§=1
- Boudreaux, K. A. (n.d.). The Parts of the Periodic Table. The Parts of the Periodic Table. https://www.angelo.edu/faculty/kboudrea/periodic/periodic_main6.htm
- K. (n.d.). O2. O2. https://cms.gutow.uwosh.edu/gutow/P-Chem_Web_Posters/KE_PM/O2/O2.html
- Watson, A., Lovelock, J. E., & Margulis, L. (1978, December). Methanogenesis, fires and the regulation of atmospheric oxygen. Biosystems, 10(4), 293–298. https://doi.org/10.1016/0303-2647(78)90012-6
- Purdue.edu https://www.chem.purdue.edu/gchelp/atoms/elements.html
- The Air We Breathe. (n.d.). The Air We Breathe. https://forces.si.edu/atmosphere/02_01_02.html
- NCI Dictionary of Cancer Terms. (n.d.). National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms
