Density

Imagine you have a box. If you put a lot of heavy things in the box, like rocks, the box will feel heavy and will be hard to lift. This is because the box is now more dense, which means that there is more stuff (mass) squeezed into the same amount of space (volume).

Density is basically how much stuff is packed into a certain amount of space. It's like trying to fit a bunch of toys into a small toy chest – the more toys you try to cram in, the more dense the toy chest becomes.

For example, a block of wood might be the same size as a block of metal, but the metal will be much heavier because it is more dense. This is because there is more mass (stuff) packed into the metal block than there is in the wood block.

So, density is how much mass (stuff) is packed into a certain amount of space (volume). And the more dense something is, the heavier it will feel.