Water and Aqueous Systems

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Water and Aqueous Systems
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Water Molecule
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Hydrogen Bonds
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Properties of Water Resulting from Hydrogen
Bonding

• High surface tension
• Low vapor pressure
• High specific heat capacity
• High heat of vaporization
• High boiling point

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Surface Properties

• Surface tension the inward pull or force the
  tends to minimize the surface area of a liquid
• Water molecules are only hydrogen bonded on one
  side and are not attracted to the air

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Water Droplets

• Surface tension holds liquids in a spherical
  shape- smallest surface area for a given volume
• Gravity flattens it
• The stronger the surface tension the more
  spherical the drop

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Surfactant

• Surface Acting Agent
• Decreases surface tension
• Interferes with hydrogen bonding

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Specific Heat Capacity

• Because of hydrogen bonding the specific heat of
  water is higher than that of most other substances

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Evaporation and Condensation

• Evaporation 2.26 kJ per gram is absorbed

• Condensation 2.26 kJ per gram is released

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Melting Points and Boiling Points of Some
Substances with Low Molar Mass
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Boiling Points and Melting Points

• Molecular compounds with low molar masses tend to
  have low boiling points

Boling Point -33.3 oC
Boiling Point 100oC
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Hydrogen Bonding in Ice
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Ice
Snowflake Symmetry is Due to Hydrogen Bonding
Ice is less dense than Water
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Solvents and Solutes

• Aqueous Solutions Water samples containing
  dissolved substances
• Solute the dissolved particles
• Solvent The medium the particles dissolve in
• Solutions are homogeneous mixtures
• Solutes can be solids, liquids or gases- ionic or
  molecular

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Like Dissolves Like

• Solvation the process that occurs when a solute
  dissolves
• H2O and NaCl
• H2O and Oil

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Electrolytes and Nonelctrolytes

• Electrolytes compounds that conduct electricity
  in aqueous solution or molten state
• ALL Ionic compounds are electrolytes
• Not all conduct to the same degree
• Nonelectrolytes dont conduct

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Water of Hydration

• The water in a crystal
• CuSO45H20
• A compound that contains water of hydration is
  called a hydrate

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Water of Hydration

• Effloresce if a hydrate has a higher vapor
  pressure than the water in the air the hydrate
  will lose water

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Water of Hydration

• Hygroscopic remove water from the air
• Desiccants drying agents (remove water from the
  air)

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Water of Hydration

• Deliquescent can remove enough water from the
  air to form a solution

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Suspensions

• Mixtures from which particles settle out upon
  standing
• Bigger particles than in a solution
• Heterogeneous

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Colloids

• Heterogeneous mixtures containing particles in
  between a suspension and a solution

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Tyndall Effect

• Particles in a colloid scatter visible light in
  all directions
• Suspensions also exhibit Tyndall effect but
  solutions NEVER do

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Brownian Motion

• Particles in a colloid viewed under a microscope
  will flash (scintillate) because of Brownian
  motion- the chaotic motion of the particles
• Caused by the collisions between water molecules
  and colloidal particles

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Emulsions

• Colloidal dispersions of liquids in liquids
• An emulsifying agent is necessary for the
  formation and maintenance of an emulsion

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