If you have ever tried piling up dry sand, you will know that you cannot get the pile to form at a steep angle. As you put more and more sand on the pile, the extra material simply slides down and although the pile gets bigger, it keeps the same angle.
But if you make the sand damp, it will stand up well, as you see when you build sandcastles.
Yet if you add too much water, the sand just flows like a liquid.
