Question

air is made up of different gases, such as oxygen, nitrogen, and carbon dioxide.
which statement best describes these three components of air?
○ oxygen, nitrogen, and carbon dioxide are all classified as pure substances.
○ oxygen, nitrogen, and carbon dioxide cannot react with another substance.
○ oxygen, nitrogen, and carbon dioxide are chemically bonded to one another.
○ oxygen, nitrogen, and carbon dioxide can be classified as elements.

Explanation:

compound substance; all meet the definition of pure substances (uniform, unchanging composition). The other options are incorrect: these substances can react with other chemicals (e.g., oxygen reacts with hydrogen), they are mixed physically (not chemically bonded) in air, and carbon dioxide is a compound, not an element.

Answer:

compound substance; all meet the definition of pure substances (uniform, unchanging composition). The other options are incorrect: these substances can react with other chemicals (e.g., oxygen reacts with hydrogen), they are mixed physically (not chemically bonded) in air, and carbon dioxide is a compound, not an element.