Does the mixture have a simple substance? What is it?
Your teacher is talking about the same kind of elements of different mixtures of substances such as oxygen O2 O3 O 2 their mixture is O2 and O3 only one element, that white is by your element with the elemental mixture
How can we say that the mixture is simple? Simple substance is pure material pure matter only one molecule and a stuff contains two or more molecules is the mixture problem is clearly unreasonable Well
Such as red phosphorus and white phosphorus, the molecular formula is P, but the structure is not the same, even if the mixture is oxygen and ozone, the molecular formula is not the same, but are composed of O elements
Of course there are myself! Such as red phosphorus and white phosphorus mixture, white tin and gray tin mixture, oxygen and ozone mixture, etc., anyway, there are a lot of it! Usually pay attention to accumulation. I hope that my answer is helpful to you and wish you good results!
