Nitrogen gas (N₂) can be converted to a solid form, known as solid nitrogen, through a process called liquefaction followed by solidification. Here's how it works:

1. Liquefaction:

- Nitrogen gas is cooled to its critical temperature, which is -146.9 °C (-232.4 °F).

- At this temperature, nitrogen gas can be liquefied by applying pressure.

- This process is typically done using a cryocooler or a Claude cycle.

2. Solidification:

- Once liquefied, the liquid nitrogen is further cooled below its freezing point of -210 °C (-346 °F).

- This can be achieved by reducing the pressure or by further cooling with a colder medium.

- As the temperature drops below the freezing point, the liquid nitrogen solidifies into a white, crystalline solid.

Properties of Solid Nitrogen:

- Non-flammable and inert: It is very stable and unreactive at room temperature.

- Very cold: Solid nitrogen has a temperature of -210 °C, making it extremely cold.

- Brittle: Solid nitrogen is brittle and can break easily.

Applications of Solid Nitrogen:

- Cryogenic preservation: Used to preserve biological samples, such as blood, sperm, and eggs.

- Refrigeration: Used in scientific research, medical applications, and food preservation.

- Industrial processes: Used in the production of electronic components, plastics, and fertilizers.

Note:

- The process of liquefying and solidifying nitrogen requires specialized equipment and safety precautions due to the extremely low temperatures involved.

- Solid nitrogen is not a common substance found in everyday life.