Point T on the diagram represents which feature?

Answer: The triple point where solid, liquid, and gas coexist Point T is at the intersection of all three phase boundary curves, which by definition is the triple point where all three phases coexist in equilibrium.

Sublimation is the direct phase change from

Answer: Solid to gas (skipping liquid) Solid CO₂ (dry ice) sublimes at room T because it lies below its triple point at 1 atm. Iodine and naphthalene also sublime at ambient pressure.

A liquid boils when its vapor pressure equals:

Answer: The external (atmospheric) pressure Boiling occurs at the temperature where vapor pressure of the liquid equals the surrounding pressure.

AP Chemistry · Topic 3.3

Solids, Liquids, and Gases Practice

Part of Properties of Substances and Mixtures.(SAP-7.A)

Practice questions

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Sample questions

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Sample 1difficulty 1/5
$Point T sits where all three phase-boundary curves intersect; point C is the labeled high-T,P endpoint of the liquid-gas line.$
$Point T on the diagram represents which feature?$
- A
  $The normal boiling point$
- B
  $The eutectic point$
- C
  $The triple point where solid, liquid, and gas coexist$
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- D
  $The critical point$
Why
$Point T is at the intersection of all three phase boundary curves, which by definition is the triple point where all three phases coexist in equilibrium.$
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Sample 2difficulty 2/5
$Sublimation is the direct phase change from$
- A
  $Liquid to solid$
- B
  $Liquid to gas$
- C
  $Gas to liquid$
- D
  $Solid to gas (skipping liquid)$
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Why
$Solid CO₂ (dry ice) sublimes at room T because it lies below its triple point at 1 atm. Iodine and naphthalene also sublime at ambient pressure.$
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Sample 3difficulty 2/5
$The vapor pressure of water is plotted against temperature; the dashed horizontal line marks 760 torr (1 atm).$
$A liquid boils when its vapor pressure equals:$
- A
  $The external (atmospheric) pressure$
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- B
  $Zero$
- C
  $Half the atmospheric pressure$
- D
  $The critical pressure$
Why
$Boiling occurs at the temperature where vapor pressure of the liquid equals the surrounding pressure.$
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Sample 4difficulty 2/5
$The dashed box labels the region beyond point C.$
$The shaded region beyond C represents:$
- A
  $Pure solid phase$
- B
  $A supercritical fluid with no distinct liquid/gas phases$
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- C
  $A metastable vapor$
- D
  $An ideal gas$
Why
$Beyond the critical point both temperature and pressure exceed Tc and Pc, producing a supercritical fluid in which the liquid-gas phase boundary disappears.$
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Sample 5difficulty 2/5
$A heating curve shows temperature vs heat added for water, with two flat plateaus.$
$What occurs along the longer second plateau (at 100 °C)?$
- A
  $Heating of liquid.$
- B
  $Melting (ice \to water).$
- C
  $Heating of steam.$
- D
  $Vaporization (water \to steam).$
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Why
$The plateau at 100 °C is vaporization. ΔH_vap is much larger than ΔH_fus, so this plateau is longer.$
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