<s>[INST] Why is one kilogram of iron heavier than one kilogram of cotton? [/INST] Your question is based on an incorrect premise. One kilogram of iron has the same mass, and consequently the same weight, as one kilogram of cotton.</s>\ <s>[INST] oh, why it is that i feel the iron is "heavier"? [/INST] It could be because the density of iron is higher than the one of cotton. Which means that 1kg of cotton takes much more space compared to 1kg of iron.</s>