Question

Which of the following is a pure substance?
a) Air
b) Distilled water
c) Steel
d) Brass

Answer 1

Distilled water is a pure substance. (option b)

• A pure substance is one that consists of a single type of molecule.

• Air is a mixture of different gases such as Oxygen, Hydrogen, carbon dioxide, water vapors, etc.
• Steel - alloy of iron and 2% carbon,1% manganese with small amounts of silicon, phosphorous, sulfur, and oxygen.
• Brass - an alloy of zinc and copper.
• Hence all these consist of more than 1 type of element or substance and are not pure.
• Alloy is mostly a metallic substance consisting of two or more elements, either in the form of a compound or solution.