Question

account for the following
a) fresh air cannot be regarded as pure substance
b) for a common man the word pure means without any adulteration but for a scientist the world pure has a different meaning why it's so explain

Answer 1

a) Fresh Air is not pure because it contain a lots of gases like oxygen,nitrogen,carbon dioxide.etc . Air is a mixture not a pure substance.

b) According to scientist a pure substance must contain same particles. For example, blood may look pure to a common man but it consist of RBC,WBC, platelets, plasma.etc. Here blood is not adulterated but it's impure(mixture) to a scientist.