A gas can be liquified by pressure alone only, when its temperature is _____ its critical temperature.
A. Less than
B. More than
C. Equal to or higher than
D. Less than or equal to
Answer: Option D.
Explanation:
Only below and at the critical point there is strong demarcation in properties of liquids and gases above the critical point we can’t recognize the difference. Hence for a gas which is under or at the critical point can be liquefied. For a gas above critical point can also undergo a pressure change but we can’t notice the difference in properties.
