Superhydrophobic sand

This gif has been blowing a few minds lately. It's superhydrophobic sand. You know how oil and water won't mix? Oil is known as a "hydrophobic" material as a result, it's "afraid" of water and the two will try to separate. As it happens, you can engineer other materials with the same property, often by sticking little oily molecular chains onto them. That gives you a material where - for example - water will roll right off it. Silica is a great substrate for this, and sand is essentially silica. 

So you can get some sand, treat it appropriately, and when it's poured into water the two simply won't mix. The water can't even get into the tiny spaces between the sand grains, so the air that's mixed in with the sand stays there as a big bubble, giving it that shiny appearance.

Now, just how hydrophobicity works is an interesting subject in and of itself. It's important not just in waterproofing, but how the proteins that your body uses can arrange themselves, and how certain drugs work. I'll be writing about that in the near future.