The Two Flat Spots

You'll learnto read a heating curve — sloped legs warm one phase, flat plateaus pull particles apart.

Put a burner under a block of ice and the thermometer climbs, then stops dead, twice, while the burner keeps burning. Those flat stretches are where the energy goes into pulling molecules apart instead of speeding them up, and the second one is nearly seven times longer than the first. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · 1.00 mol H₂O · ΔH_fus = 6.01 kJ/mol · ΔH_vap = 40.7 kJ/mol · v5

sloped legs warm one phase · flat plateaus separate two

Before you start

What you're looking at

A heating curve for one mole of ice at 1 atm: temperature up the page, energy added across it, so a segment's length is what it costs.

The question

Why does the thermometer stop dead twice while the burner keeps burning?

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