🧊, 💧, 💨 Phase Diagram Flashcards
(6 cards)
Is it possible to melt the solid by keeping the temperature constant and only increase the
pressure? Explain why or why not
No, because the Solid ⇌ Liquid does not cross the temperature line going thru the normal melting point
Is it possible to boil a liquid at a temperature below its normal boiling point by changing the pressure? Explain using the phase diagram.
Yes. According to the phase diagram, lowering the pressure lowers the boiling point. The normal boiling point occurs at 1 atm, but if you decrease pressure below 1 atm, the liquid can boil at a lower temperature. This is how water boils at lower temperatures at high altitudes.
At the triple point, all three phases coexist. What would happen if you increase the temperature while keeping pressure constant at the triple point?
If you increase the temperature while holding pressure constant at the triple point, the substance will move from the triple point into the liquid + gas region, meaning the solid will melt and the liquid will begin to evaporate. Eventually, only the gas phase will remain.
Can a gas be converted directly into a solid by changing pressure and temperature? Explain using the phase diagram.
Yes. This is called deposition. If you lower the temperature and increase the pressure appropriately, the gas can move across the gas–solid boundary on the phase diagram and become a solid without becoming a liquid.
Is it possible for a substance to exist as a liquid below its triple point temperature? Explain your reasoning.
No. Below the triple point temperature, the liquid phase cannot exist, regardless of pressure. The substance will transition directly between solid and gas (sublimation or deposition), since the triple point is the minimum condition for liquid stability.
What happens if you try to increase the pressure of a gas above its critical point?
Above the critical point, there is no distinct phase boundary between liquid and gas — the substance becomes a supercritical fluid. Increasing the pressure just increases the density, but you cannot condense the gas into a liquid unless you also lower the temperature below the critical point.
