We'll take a break from dino bites today to answer a question from Max McGrath and Perrin Shepherd, two of COSI's fine educators. They saw some youtube videos about liquidized sand wanted to know, with good reason, what in the world was going on.
Normal sand can behave in some liqiudy ways; for example, it flows and it takes the shape of its container. But it also acts like a solid - it's kind of hard to make a watercastle. These different properties are governed by the friction between the individual grains. The more the sand grains can move freely around each other, the more the collective will act like a pure liquid.
If you pump a bunch of air through a bed of sand, the drag from that air can lift and mix the grains, separating them from their usual constant contact. The reduced friction gives the sand bed some surprising properties, like suspended objects sinking or floating.
You could almost say that the states of matter are...fluid.