Question

True or False: Solid substances directly evaporate from the solid phase above the critical point.

a) True
b) False

Answer 1

The statement is false; above the critical point, a substance exists as a supercritical fluid, not a solid or gas. Solid directly to gas transition below the triple point is known as sublimation.

Step-by-step explanation:

The statement 'Solid substances directly evaporate from the solid phase above the critical point.' is False. Above the critical point, a substance does not have a distinct liquid or solid phase; it exists as a supercritical fluid. The process of solid substances turning directly into gas without passing through the liquid phase under certain conditions is known as sublimation. Sublimation occurs at temperatures and pressures below the substance's triple point. Examples include dry ice subliming into carbon dioxide gas and frost forming on cold windows from water vapor.