The box with the rocks will be much heavier becasue it has more MASS packed into the same volume. This means it has a higher DENSITY.

The unit used to measure density is typically grams per cubic centimeter, or grams per cubic meter. For example, water has a density of 1 g/cm³ , which means that one cubic centimeter of water weighs one gram.

Density can help us identify substances and even determine their purity. Different meterials have different densities. For instance, wood is less dense than iron because it has less mass packed into the same volume.

The property (or characteristic) of density allows us to predict wheter something will float or sink in a liquid.
Objects with a density greater than that of the liquid will sink.
Objects with a density less than that of the liquid will float.

In everyday life, density plays a very important role. For example, it helps engineers design ships and submarines that can float and carry heavy loads without sinking. It also explains why ice floats on water - ide is less dense than liquid water, so it stays at the surface of the water.

Understanding density opens doors to understanding many phenomena in the world around us. It is a key concept in physics, chemistry, and engineering that helps us make sense of the physical properties of matter.