Fri September 23, 2011 By: Simran Handa

ma'am it's written in one of the refreshers of chemistry that water is a pure substance as it has only one kind of molecule.I somehow disagree with this as water consists of 2 molecules of hydrogen and 1 molecule of oxygen. As it is said that a mixture is a combination of two or more pure substances then why is still water called a pure substance even though it is a combination of two different elements?

Expert Reply
Sun September 25, 2011
Once the molecules of Hydrogen and Ocygen have reacted to form water, they have loosed their individual properties. So, a new molecule is formed which is H2O. 
Water is a pure substance but it is a compound and is made of oxygen and hydrogen.

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