Boiling Point

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Boiling Point
By Mark Ioannidis Meghan Kane Keith
Sheridan AJ Gray Steve Rodillico
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Overview

• How a Liquid reaches Boiling Point
• Vapor Pressure
• Changes in Boiling Point
• Boiling and Evaporation
• Heat Source

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How a Liquid Reaches Boiling Point

• Rate of evaporation of a liquid increases as heat
  is added.
• When heat is added a larger number of particles
  at the liquids surface are able to vaporize.
• The particles left over begin to move faster and
  faster as they absorb more heat.
• Their average kinetic energy increases.

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How a Liquid Reaches Boiling Point

• When the average kinetic energy increases the
  liquids temperature.
• When the liquid is heated to a high enough
  temperature, many particles throughout the liquid
  have enough kinetic energy to vaporize.
• This point, when there is vaporization throughout
  the liquid, is when boiling occurs.

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How a Liquid Reaches Boiling Point

• All matter has a certain amount of atmospheric
  pressure pushing against it.
• Boiling Point is reached when the amount of vapor
  pressure of the substance is equal to the amount
  of atmospheric pressure placed against it.
• When they are equal, vapor bubbles are produced
  and escape into the air as the liquid boils.
• The bubbles that are first to escape are the ones
  containing the highest kinetic energy.

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Vapor Pressure

• Vapor pressure is the force produced by the gas
  above the liquid.
• When a liquid is sealed into a container, some of
  the particles in the substance vaporize, which
  then build up a force as the collide with the
  walls of the container. This force is known as
  vapor pressure.
• Although the vapor has the same kinetic energy as
  the liquid its stored energy is much higher.

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http//www.elmhurst.edu/chm/vchembook/images2/163
boiling.gif
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Definition

• Boiling point is the temperature at which the
  vapor pressure of the liquid is just equal to the
  external pressure.
• At boiling point, bubbles of vapor form
  throughout the liquid, rise to the surface, and
  escape into the air as the liquid boils.

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http//hyperphysics.phy-astr.gsu.edu/hbase/kinetic
/imgkin/vapp4.gif
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Changes in Boiling Point

• Boiling Point of a liquid changes as the external
  pressure changes.
• Normal Boiling Point- the boiling point of a
  liquid at a pressure of 101.3kPa.

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Chemistry Addison - Wesley pg 278 Table 10.10
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Changes in the Boiling Point

• The Boiling point decreases at lower external
  pressures because particles need less kinetic
  energy to escape the liquid.
• The Boiling point increases at higher external
  pressures because particles need more kinetic
  energy to escape.

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Boiling and Evaporation

• Boiling is a cooling process similar to
  evaporation.
• In boiling, like evaporation, the particles with
  the highest kinetic energy escape first when the
  liquid is at boiling point.

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Heat Source

• Turning off the external heat source drops the
  liquids temperature below boiling point.
• Supplying more heat allows more particles to gain
  enough kinetic energy to escape.
• Temperature of the boiling liquid never rises
  above boiling point.
• If heat is supplied at a greater rate, the liquid
  only boils faster.

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http//www.heartmagic.com/zzBoil1.jpg
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References

• Chemistry - Addison Wesley pgs 277-279
• http//www.elmhurst.edu/chm/vchembook/163boilingp
  t.html
• http//hyperphysics.phy-astr.gsu.edu/hbase/kinetic
  /vappre.html

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Acknowledgements

• Wed like to thank the group members for their
  contributions and hard work put into this
  presentation. Thank you for your time and
  attention.