Distinguish between vapor and gas.

Two different gases $A$ and $B$ are filled in separate containers of equal capacity under the same conditions of temperature and pressure. On increasing the pressure slightly,gas $A$ liquefies,but gas $B$ does not liquefy even on applying high pressure until it is cooled. Explain this phenomenon.

$A$ real gas cannot be liquefied in which of the following conditions?

The gas with the highest critical temperature is

What happens when the temperature of $CO_2$ at its critical temperature of $30.98 \, ^\circ C$ is increased or decreased?

Under what conditions can an ideal gas,which follows the kinetic gas equation,be liquefied?