Aheating curve has two flat lines, or plateaus. what does the plateau at the lower temperature represent?

a) boiling of a liquid
b) melting of a solid
c) increase in temperature of a substance
d) decrease in temperature of a substance

B) Melting of a solid.

Explanation:

Kindly, see the attached image.It is known that the substance has different 3 phases (solid, liquid, and gas).By heating, the substance converted from solid phase to liquid phase passing by a plateau that represents equilibrium between the two phases.By further heating, the solid completely converted into liquid phase, then converted to gaseous phase passing by a plateau that represents an equilibrium between the liquid an gaseous phase.

The plateau at the lower temperature represent: B) Melting of a solid.

The air is going to come out because of the low pressure.

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