Answer:
A catalytic converter changes nitrogen dioxide to nitrogen gas and oxygen gas is a chemical change.
Explanation:
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In this case, since physical changes do not modify the molecular composition and structure of the material undergoing it whereas the chemical change does, for catalytic converters we should know they promote chemical reaction in which the composition is changed; for instance, for the given example, the following chemical reaction is the evidence:

As you can see, nitrogen and oxygen are no longer bonded but separated by themselves, therefore, this is a chemical change.
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Answer:
This reaction is sometimes referred to as the Baeyer test. Because potassium permanganate, which is purple, is reduced to manganese dioxide, which is a brown precipitate, any water‐soluble compound that produces this color change when added to cold potassium permanganate must possess double or triple bonds.
Explanation:
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