In chemistry, which of the following best defines the concept of "purity" in a substance?
A) Purity refers to the ability of a substance to dissolve in a given solvent, indicating its chemical activity.
B) Purity describes the extent to which a substance is free from contaminants or other substances, ensuring that it consists of only one chemical species or compound.
C) Purity is the measure of a substance's color intensity, used to identify its chemical composition.
D) Purity denotes the total volume of a substance when mixed with another substance, affecting its concentration.