At the critical temperature , the substance exists as a

Options

A. liquid
B. gas
C. both (1) and (2)
D. fluid

Answer

D

Explanation

When liquid is heated in a closed vessel , vapor pressure increases continuously. At first , a clear boundary is visible between the liquid and vapor phases because liquid is more dense than vapor. As the temperature increases , more vapor rises. At the same time , liquid becomes less dense. It expands because the molecules move apart. When the density of liquid and vapors becomes the same, the clear boundary between liquid an dvapors disappears. This temperature is called critical temperature. At the critical temperature , there is no fundamental distinction between a liquid and a gas - we simply have a fluid.
Note that intermolecular forces are independent of temperature, the kinetic energy of molecules increases with temperature.