Respuesta :
A pure substance has a definite and constant composition — like salt or sugar. A pure substance can be either an element or a compound, but the composition of a pure substance doesn't vary.
Answer:
A substance with precise melting and freezing point.
Explanation:
A pure substance is one that has a precise melting and freezing point
Like water, pure water boils at 100C while impure water will boil at a temperature less than that.
Impurity also affects the refractive index and specific gravity of a substance