This guy builds rockets with bottles and water, adding liquid nitrogen, turning them upside down and boom, instant propulsion: The nitrogen expands very fast on top of the warmer water, turning violently into gas, and pushing the bottle up.
https://www.youtube.com/watch?v=43vvwB9GNcA
And in case you worry about how he’s handling liquid nitrogen—I did too—apparently it’s not that dangerous thanks to the Leidenfrost effect, which creates an insulating layer of gas as soon as the liquid nitrogen drops touch his warm skin. As long as he doesn’t submerge his hand, he’s safe. Ish.
