This question has no definitive answer because there are no volumes given.
1kg of iron contains more matter and occupies less space than 1kg of cotton. Iron is denser than cotton, so it has a higher mass-to-volume ratio.
Cotton wool is less dense than iron, meaning it takes up more space for the same mass. Iron is much denser and therefore occupies less volume compared to the same mass of cotton wool.
sand is more denser than cotton
Lead is denser than iron.
Lead is denser than iron. Lead has a density of 11.34 g/cm^3, while iron has a density of 7.87 g/cm^3.
iron is much denser than water. So, steel is denser, too, because it is made from iron.
Iron plate is denser than feather. Densities of materials are typically measured in terms of mass per unit volume, so iron plate, being a metal, is much denser than a feather, which is made of lightweight keratin.
It means that mercury is denser than iron.
0.4
The density of Iron is a property of the Iron itself, and not related to how much you have of it.
When we say that 1 kg of iron / cotton, we mean that it is the apparent weight. As they are already displacing air and by Archimedes' Principle they both are acted upon by the buoyant force directly proportional to the weight of air they displaced, and cotton displaces more air, therefore its actual weight is more than actual weight of iron.
After heating iron in air iron oxides are obtained; these oxides have a lower density than iron.