What is the surface tension at the critical temperature?

Explain the liquefaction of $CO_2$ gas using the Thomas Andrews plot,including the effects of temperature and pressure,and define the critical constants.

Which among the following gases liquefy easily?

Which of the following gases has the highest critical temperature?

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

What is the value of the critical temperature of water (in $K$)?