HEATING AND COOLING CURVES

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HEATING AND COOLING CURVES

• Harry S. Truman High School Chemistry Department

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What are some things that happen as we heat a
sample up?

• Solid ? Liquid ? Gas
• Melting, Evaporating
• Increase in entropy

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What is heat? How is heat different from
temperature?

• Heat is a measure of kinetic or translational
  energy
• In chemistry heat is measure in Joules (J)
• Heat is dependent on mass, temperature change and
  specific heat (or ability of a substance to
  absorb heat)
• Temperature is a measure of warmth or coldness.
• Temperature is independent of heat
• Temperature is measured in Kelvin (K) or Celsius
  (C)

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What is the heating curve?

• The heating curve is a graph which represents how
  a sample changes phases. As heat is added over
  time, the sample changes temperature and phase
  accordingly. Thus heating curve.

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How does the heating curve look?
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What are the parts of the heating curve?
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What are the parts of the heating curve?
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What are the parts of the heating curve?
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What are the parts of the heating curve?
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What are the parts of the heating curve?
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What are the parts of the heating curve?
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Why is the curve flat at some portions?

• Temperature is staying constant, but potential
  energy is decreasing
• During this time the solid completely becomes
  liquid (or liquid becomes solid)

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Why is the curve flat at some points?

• This is called the heat of fusion (Hf) in segment
  BC and heat of vaporization (Hv) in segment DE.
• Remember fusion is melting and vaporization is
  evaporation

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What is heat of fusion? What is heat of
vaporization?

• Hf is the amount of energy needed to completely
  make a solid into a liquid
• Hv is the amount of energy needed to completely
  make a liquid into a gas

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Summary

• The heating curve is a useful tool to show us the
  changes in temperature, energy, and entropy as a
  sample is heated up. It give us detailed
  information about phases and phase changes of
  samples.