Science Trick

Blake: Mommy, I need your help with a science trick.
Me: Okay, what do you need?
Blake: Can you give me some fire to put on the end of this stick?
Me, a little surprised at this request: Well, no, I can't give you fire because... (insert long explanation)
Blake bursts into tears and leaves the room to pout. Five minutes later, he returns looking quite cheerful.
Blake: Okay, I have a new idea. First I need a cup and some water. Oh, and I need a teaspoon, and a bowl.
Proud that he's pulled himself together, I'm happily providing all he asks and getting ready for us to make some cookies or whatever he has planned.
Blake, in a sweet little voice: Mommy, do we have any liquid nitrogen?