If the element is oxidized, then it's oxidation number would increase.
Let's say we have the following reaction.
2H2O --> O2 + 2H2
To the left, the oxidation number of O is -2, as it is bonded to two H, which is always H+. To the right, we have O2, and all gases have a oxidation number of 0 (zero). We say that O has been oxidized.
The answer is D. The final substance in Beaker X is a mixture and in Beaker Y is a pure substance.
The question tells us that the sugar is not visible. This is because it is soluble. The sugar has dissolved into the water, making the two a mixture. The sand, on the other hand, is not dissolved at all. The water and sand are two separate pure substances.
Although I’m not entirely sure what answer you’re looking for, I’d say because most scientific investigations require multiple trials of an experiment
Oxygen atoms are all different whereas hydrogen atoms are the same but also lighter
