Balls of science is a dramatic way to explain phase change, and the consequences of catastrophic failure of the vessel containing the process. As a general rule, Star Trek metaphors work well in this crowd, and what we are doing here is really a containment breach of the reactor core. If the core was water bottle, and antimatter was liquid nitrogen. It’s a good demonstration of volume and pressure relationships.
It makes good sense that the more gas you place in an enclosed vessel the more pressure you will develop inside of it. Robert Boyle confirmed this in the 16th century and expressed in mathematically, basically saying that the volume of gas is inversely proportional to the pressure exerted upon it. Conversely, the greater the volume of gas, the more pressure it will exert upon whatever is holding it. This demonstration starts with a fixed volume, namely that of the inside of the water bottle. Liquid nitrogen is added to it, and bottle is sealed. Liquid nitrogen has a boiling point of -196 degrees celsius. When exposed to temperatures above that it changes phase to a gas. Along with that phase change is a substantial change in volume. One litre of the stuff will make 694 litres of gas. If we follow Boyle’s law we know that the pressure in the bottle will increase substantially, until something gives. In this case, the bottle will rupture releasing pressurized nitrogen very rapidly.
Gassous nitrogen makes up almost 79% of atmosphere.