Density is an intensive property because it is defined as the ratio of two extensive properties: mass and volume. Both mass and volume depend on the amount of matter present (they are extensive properties), but when mass is divided by volume, the resulting ratio (density) is independent of the quantity of the substance. Thus, density remains the same regardless of the size or amount of the sample, making it an intensive property.
More specifically, if a system is divided into parts, each part will have the same density as the whole, even though the mass and volume of each part are smaller. This invariance with respect to the size or amount of the material confirms density as an intensive property.
In summary, density is intensive because it does not change with the amount of matter; it is a ratio of two extensive properties that cancels out the dependency on size or quantity.
