You have a bag of cotton and a bar of iron,each indicating a mass of 100 kg when measured on weighing machine.In reality,one is heavier than the other. Can you say which is heavier than the other?and why?????/

Density of iron is more compared to the density of cotton. This is obvious because 1 kg of cotton occupies huge volume compared to 1 kg of iron. So, iron is denser than cotton. Or we say, iron is heavier than cotton