we say that when all constituent particles of a substance are same in chemical nature ,it is said to be pure substance. but in case of glucose molecule all the atoms are different then what sense we call it pure substance although it has fixed proportion but can plz clearify the definition of pure substance and in what context it says that substance are same in chemical nature.
Answers
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.
Mixtures are physical combinations of pure substances that have no definite or constant composition — the composition of a mixture varies according to who prepares the mixture.
Although chemists have a difficult time separating compounds into their specific elements, the different parts of a mixture can be easily separated by physical means, such as filtration.
For example, suppose you have a mixture of salt and sand, and you want to purify the sand by removing the salt. You can do this by adding water, dissolving the salt, and then filtering the mixture. You then end up with pure sand. Mixtures can be either homogeneous or heterogeneous