Critical temperatures for $A$,$B$,$C$ and $D$ gases are $25\,^{\circ}C$,$10\,^{\circ}C$,$-80\,^{\circ}C$ and $15\,^{\circ}C$ respectively. Which gas will be liquefied more easily?

Gases can be liquefied by:

Which statement$(s)$ is/are applicable above critical temperature?

Why does the boundary between the liquid phase and the gaseous phase disappear upon heating a liquid up to the critical temperature in a closed vessel? In this situation,what will be the state of the substance?

Gases possess characteristic critical temperature which depends upon the magnitude of intermolecular forces between the gas particles. Critical temperatures of ammonia and carbon dioxide are $405.5 \ K$ and $304.10 \ K$ respectively. Which of these gases will liquefy first when you start cooling from $500 \ K$ to their critical temperature?

Explain the liquefaction of real gases and permanent gases.