A few months ago, Buzzfeed posted a list titled “21 Reasons Why You Should Have Paid Attention In Science Class,” composed of a bunch of cool, weird sciencey gifs. My initial reaction was, “Okay, pretty neat, but what am I actually seeing here?” Plenty of comments on the post echoed that thought, but Buzzfeed still hasn’t answered the cries of the writhing, curious masses.

I figure it's about time to take matters into my own hands and start explaining these things, starting with the ones from the original list that I can figure out or trace back to their sources. Best case scenario, that gives us 21 cool gifs. Obviously, that’s not all the cool science gifs out there, so if you find any sciencey gifs or images that make you say, “Huh? What the heck is going on there?” send them my way!

Anyway, here’s our second gif, featuring an explosive act of tickling.

Image and video hosting by TinyPic

What the heck is going on here?

The stuff that’s blowing up is a compound called nitrogen triiodide (NI3). It’s a black powder that’s formed by adding iodine crystals to a concentrated solution of ammonia in water. When it's wet, it’s stable. When it dries, though, it’s very unstable and the lightest touch can cause it to detonate and produce a dark purple cloud of iodine vapor.

What you see here is a common demonstration of that instability: A wet filter paper smeared with NI3 and allowed to dry while held by a ring stand. A light brush with a feather then sets it off. In this gif, you get more bang for your buck with two samples of NI3 set one above the other. The force from the explosion of the first sample causes the other one to detonate. In the video below you can see the same reaction and hear the sharp noise that the explosion makes.