Gases can be liquefied by

Gases can be converted into a liquid state through the process of liquefaction. This transition is achieved by applying high pressure and reducing the temperature (cooling).

• Applying Pressure: Increasing the pressure forces gas molecules closer together by reducing the intermolecular space between them.
• Reducing Temperature: Lowering the temperature decreases the kinetic energy of the gas molecules. When the kinetic energy is sufficiently reduced, the attractive intermolecular forces (such as Van der Waals forces) can overcome the motion of the particles, binding them together into a liquid state.

Every gas has a critical temperature; if the temperature is above this point, the gas cannot be liquefied no matter how much pressure is applied. Therefore, both cooling and compression are fundamental to the process.