To make a snow cone with nitrous gas, as an experiment, you will need the following: liquid nitrogen, protective gear, a bell jar, and a dish to hold the liquid nitrous.
While wearing protective equipment, pour liquid nitrogen into a dish. Place it in a bell jar. Now, turn on the vacuum, until it freezes. The snow only lasts for a small bit of time, because it melts immediately upon having contact with the air. When you turn the vacuum off, it will immediately melt. When you turn it...