How can you prove that air exists between solid particles?

You can prove that air exists between solid particles using a simple experiment. For instance, if you take a container filled with small solid particles, like sand, and pour water over them, you'll observe that the water doesn't fill the container completely. This is because the air trapped between the particles prevents the water from occupying all the available space, demonstrating the presence of air in the gaps between the solids. Additionally, techniques like measuring the volume of solid particles before and after adding water can quantitatively show the volume of air present.