States of Matter

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States of Matter

• States of Matter
• Heating Curve
• Factors Affecting State
• Vapor Pressure

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Defining States
Has Own Shape? Has Own Volume?
Solid
Liquid
Gas
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Elements and State
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Changes of State
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Changes of State
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Changes of State

• Endothermic
• Heat H2O(s) ? H2O(l)
• Heat H2O(l) ? H2O(g)
• Heat H2O(s) ? H2O(g)
• Exothermic
• H2O(g) ? H2O(l) heat
• H2O(l) ? H2O(s) heat
• H2O(g) ? H2O(s) heat

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States of Matter

• States of Matter
• Heating Curve
• Factors Affecting State
• Vapor Pressure

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Heating Curve
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Heating Curves

• Added heat will be used in one of two ways
  NEVER BOTH
• To raise the temperature of a sample graph line
  goes UP!
• To overcome IMF so that particles separate from
  each other graph line remains FLAT!

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Change of State

• Since the curve plateaus when a change of state
  occurs, the flat line can be used to find the
  temperature at which the change occurs.
• Melting / Freezing occur at the SAME temp.
  (freezing point, FP)
• Boiling / Condensation occur at the SAME temp.
  (boiling point, BP)

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Temperature Points

• Boiling Point (BP) is a temperature!
• - boiling begins if heating
• - condensation begins if cooling
• Freezing Point (FP) is a temperature!
• - freezing begins if cooling
• - melting begins if heating

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Phase Equilibrium

• Each plateau represents a region of equilibrium
• At that temperature, if no heat is added or
  removed, the rates of.

• freezing and melting are equal.
• Vaporization and condensation are equal.

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Cooling Curve
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Heat of Fusion

• Heat of fusion (Hfus) the amount of heat
  required to melt a sample
• q m Hfus
• How much heat is required to melt 9.32 g of solid
  water?

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Heat of Vaporization

• Heat of vaporization (Hvap) the amount of heat
  required to vaporize a sample
• q m Hvap
• How much heat is required to evaporate 9.32 g of
  water?

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Heat and Phase Change

• The heat/gram given off when a sample is frozen
  is the same amount required to melt the same
  sample.

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Heating Curve

• There are 5 line segments
• Solid temp. rising (q mC?T)
• Solid-Liquid crystal structure breaking apart (q
  mHfus)
• Liquid temp. rising (q mC?T)
• Liquid-Gas molecules escaping (q mHvap)
• Gas temp. rising (q mC?T)

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Heat Calculations

• What amount of heat is needed to change 5 grams
  of ice at -20oC to steam at 125oC?
• (Hint!)

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States of Matter

• States of Matter
• Heating Curve
• Factors Affecting State
• Vapor Pressure

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Temperature

• As temperature increases, motion of the particles
  increases.
• As motion increases, the sample will gain enough
  energy to change
• Solid ? Liquid ? Gas

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Pressure

• A gas is very compressible
• Under enough pressure it can be liquefied.

• Even more pressure can create a solid

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Phase Diagram

• A phase diagram combines the effects of
  temperature and pressure

As temperature increases, the phases
change Solid ? Liquid ? Gas
As pressure increases, the phases change Gas ?
Liquid ? Solid
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• Triple point all 3 phases exist
• Critical point substance cannot exist as liquid
  at any pressure past this temperature

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Phase Diagram for Water

• Unique because solid changes to liquid as
  pressure increases.

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Solid Water
Water crystals take up more space than the liquid
form
Increased pressure crushes the crystal to liquid
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Unusual Phase Diagrams
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Intermolecular Forces

• Intermolecular forces (IMF) attraction that
  occurs between molecules
• Intramolecular forces the attraction that occurs
  between atoms IN the molecule

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IMF

• There are 3 types of IMF of different strengths.
• London Dispersion Forces (weakest)
• Dipole-Dipole
• Hydrogen Bonding (strongest)

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London Dispersion Forces

• Uneven distribution (dispersion) of the electrons
  causes an
• Instantaneous dipole a particle has a positive
  pole and negative pole only for an instant

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London Dispersion

• One dipole can induce another dipole for a
  ripple effect.
• Very weak occurs mostly in gases

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London Dispersion

• Gas molecules tend to
• Have nonpolar covalent bonds
• Have symmetry
• There is no existing polarity in the molecule

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Dipole-Dipole

• Dipole-dipole the force of attraction that
  occurs between 2 polar molecules
• In this case the poles are permanent, not
  instantaneous.

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Dipole-Dipole

• Substances that experience dipole-dipole
  attraction tend to be gases or liquids.

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Hydrogen Bonding

• Hydrogen bonding exists whenever hydrogen is
  bonded toN, O, or F
• It is a stronger dipole than most polar molecules
• Therefore the attraction
• between molecules is
• stronger

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Hydrogen Bonding

• Water is the most common example of hydrogen
  bonding.
• Attraction occurs between
• the negative oxygen in
• one molecule and the
• positive hydrogen in
• another.

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Substances that experience strong
H-bonding tend to be liquids.
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Special Properties of Water

• Surface tension occurs due to the strong
  H-bonding between water molecules

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Special Properties of Water

• Capillary action due to the attraction of polar
  H2O to polar glass molecules

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Hydrogen Bonding

• NH3 and H2O experience hydrogen bonding.

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• Which has hydrogen bonding and which has
  dipole-dipole?

Hint Look for H bonded to O!!
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Recap - IMF

• There are 3 types of IMF of different strengths.
• 1) London Dispersion Forces (weakest)
• substances are gases
• 2) Dipole-Dipole (moderate)
• substances are gases/liquids
• 3) Hydrogen Bonding (strongest)
• substances are liquids

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More Forces

• There are 2 more forces that exist between
  particles.
• Van der waals forces attraction between positive
  nucleus of one atom and electrons of another
• (exceedingly weak and fleeting)
• London Dispersion ? Dipole-Dipole ? H-bonding
• Ionic bonding attraction between cation and
  anion
• (exceedingly strong substances tend to be
  solids)

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Intermolecular Forces
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Intermolecular Forces
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States of Matter

• States of Matter
• Heating Curve
• Factors Affecting State
• Vapor Pressure

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Vapor Pressure

• Vapor pressure the pressure of a vapor over its
  liquid

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Vapor Pressure Equilibrium

• Rate of vaporization Rate of condensation

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VP and Temperature

• Vapor pressure varies exponentially with
  temperature.
• More heat applied
• provides the energy
• needed for molecules
• to escape their
• liquid.

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VP and IMF

• Molecules that have STRONG intermolecular forces
  cannot easily escape their liquid.
• ? they have LOW vapor pressure

1. Which substance has the greater VP?
2. Which substance has the stronger IMF?

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Vapor Pressure

• Vapor pressure can
• be considered with an
• open container
• Then, it can be
• thought of as the force
• with which molecules
• escape their liquid

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Vapor Pressure and BP

• The atmosphere exerts a pressure on the surface
  of the earth of about 15 lbs./in2
• This pressure works to prevent molecules from
  escaping their liquid when in an open container

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Vapor Pressure and BP

• When VP exerts as much force as atmospheric
  pressure, a liquid will boil.
• Boiling point the temperature at which
• VP atm pressure
• A liquid is in equilibrium with it gas

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Vaporization

• The difference between evaporation and boiling.

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Boiling Point

• Atmospheric pressure is lower at higher
  elevations.
• ?it takes less energy to reach the boiling point
• The BP is lower