When a cup is filled with pebbles, the empty space (volume) inside the cup is partially occupied by the pebbles. But there are still tiny spaces between the pebbles.If you then pour water or sand, those fill the gaps—showing that the space is not fully solid, and matter can exist in layers or levels of occupation.Scientific ConceptThis shows that solids like pebbles don’t occupy every single space, and other substances like liquids or powders can fill in the gaps.