Actually, it's really neither. Because nitrogen comes in three forms: it's originally gas, then it's liquid nitrogen, then it gets mixed with others and becomes solid. Although, it's original form is truly gas.
At room temperatures, Nitrogen is a GAS At below 437 Degrees F. it is a liquid. It has never been down near zero degrees Kelvin. that is absolute zero. Liquid Nitrogen is used in Rocket Science for...
Nitrogen naturally occurs as a gas, but when it hits coler than -196 Degrees Celsius it then goes into liquid form. It freezes at temperatures lower than -210 degrees celsius