Energy of Phase Changes

AP Chemistry· difficulty 2/5

The graph shows temperature versus heat added for a pure substance.

heat added T A B C D E

Along which segment of the heating curve does the substance undergo melting (solid to liquid)?

  • A

    Segment C

  • B

    Segment E

  • C

    Segment B

    check_circle
  • D

    Segment A

Explanation

Flat segment B (first plateau) represents the solid-liquid phase change at constant T while heat is absorbed as ΔHfus.

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