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Heating and Cooling Curves

≈ 25 min
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If you heat a solid steadily and plot temperature against time, you get a heating curve with flat steps:

  • The temperature rises while the substance is in one state (particles speed up).
  • The temperature stays flat during a change of state, even though heating continues. The energy is going into breaking the forces between particles, not raising the temperature.

The first flat step is at the melting point; the second is at the boiling point. A cooling curve is the mirror image: flat steps where the substance freezes and condenses.

On a heating curve, what does a flat (horizontal) section represent?

While ice is melting at 0 ∘C0\,^\circ\text{C}, you keep heating it. The temperature of the ice–water mixture…

On a heating curve for water, the second flat step occurs at the substance's ______ point. (one word)