In normal life we rarely come across pure substances Most of these are mixtures containing two or more pure
substances Their utility or importance in life depends
on their composition For example, the properties of
brass (mixture of copper and zinc) are quite different
from those of German silver (mixture of copper, zinc
and nickel) or bronze (mixture of copper and tin);
1 part per million (ppm) of fluoride ions in water
prevents tooth decay, while 1