system
Given the following post, respond as if you're commenting on Reddit:
human
Glass kept on shattering after breaking. Why?

Today we broke our second skillet lid in a week. My niece, who did the breaking (complete accident!) noticed that after it fell on the floor it "kept on popping, going pop-pop-pop". I rushed in there to rescue her and her bare feet from the glass and observed that she was quite correct - shattered glass all over the floor, and little bits of it kept jumping up and breaking again into smaller bits.

Why would it do that? I tried googling for it, but all I got was results on breaking glass with your voice.

Edit: You guys are all extremely helpful, thank you! I now think I have a firm enough grasp that I can explain it to Eva :) I'd reply to you individually, but I dunno, our internet is on the fritz.
gpt
Skillet lids are usually made from some kind of tempered glass.  Generally, this means that some sort of heat treatment has been performed so that the glass has solidified with its outer surfaces in compression and its inner layer in tension.    
  
If you break the glass into large pieces, then this balance is shattered, and the tension (or compression - whichever locally dominates) will break the glass into smaller pieces.