Analyzing Heating Curves II

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​We need to be able to tell what phases are present, and what is happening, in each segment

​We know that solid is present at the lowest temperature, liquid in between, and vapor at highest temperature.

Label the 3 sloping sections with these 3 phases

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First, let's identify phases

​Remember that temperature can go up ONLY when a single phase is present.

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If more than one phase is present, the phase is changing, and rearranging particles takes up all of the energy

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First, let's identify phases

​Solid

​Liquid

Vapor

Flat segments (plateaus) mean the phase is changing.

TWO phases must be present; matter is changing from one form to the other.

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Recall that the flat segments were the surprising result in our experiment

Since substances melt at a lower temperature than they boil, the lower temp plateau is melting (solid + liquid); the higher is vaporization.

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Recall that the flat segments were the surprising result in our experiment

​Solid + liquid (melting)

​liquid

+ vapor

(vaporization)

​Vapor is a state of matter (a.k.a. gas)

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Vaporization is the change from liquid to vapor

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If the section of curve is sloped, temperature is changing. We say the phase is heating up.

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​In a cooling curve, energy is transferred OUT of the system, the slope is downward, and we say the single phase is cooling down.

If the section of curve is flat, a phase change must be occurring. Is it melting or vaporization?

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​In a cooling curve, the higher-energy phase change is condensation, and the lower-energy change is freezing.

Always remember

An increase in temperature means an increase in particle speed. This means that energy that is transferred into the system is getting stored in the motion of particles.

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A change in phase means a change in how particles are arranged! During a phase change, energy is getting stored in the arrangement of particles.

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