Solving part-1 only
#1
KMnO_4
- Transition metal is Manganese (Mn)
#2
Actually it's the oxidation number of Mn
Let's find how?




- x is the oxidation number
#3
- Purple as per the color of potassium permanganate
#4

They have the same density because a material, no matter how much of it there is, will always be a certain density. A 40g ball of iron has the same density as a 1g ball of iron.
When gas molecules condence they become a liquid and if the liquid molecules condence they turn into a solid but the solid molecules cannot condence