Final answer:
Liquefaction of gases, such as liquefied petroleum gas (LPG), occurs when the pressure overcomes the strength of the container and releases the contents. It is caused by cooling and compression of the gas, leading to the molecules condensing into a liquid form.
Step-by-step explanation:
Liquefaction of gases occurs when the pressure in a liquefied petroleum gas (LPG) container overcomes the strength of the weakened steel and the container shell separates and releases the contents. This is caused by the cooling and compression of the gas, which leads to the gas molecules losing sufficient kinetic energy to overcome intermolecular attractive forces and condensing into a liquid form. The container's inability to expand and the increased frequency of gas molecules striking the inside walls of the container lead to the pressure inside the container increasing.