Hello! It is true that water boils at 100% C, however, this is not true for any substance. Take steel, for instance, steel would take MUCH higher temperatures to melt, and to boil. As it says "ANY SUBSTANCE" this would be false.
HUNDRED GRAMS too because of the law of conservation of mass. The law of conservation of mass states that mass is neither created nor destroyed. So both sides will have the same mass