Water and Aqueous Systems
Chemistry / Honors Chemistry
North Henderson High School
15.1 -- Water and Its Properties
Essential Question:
What accounts for the high surface tension
and low vapor pressure of water, and how
would you describe the structure of ice?
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Polarity of Water
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Hydrogen Bonding in Water
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Water in the Liquid State
• Many unique and important
properties of water result
from hydrogen bonding:
– High surface tension
– Low vapor pressure
– Six-sided ice crystals
– High boiling point
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Surface Tension
• Is steel more dense than water?
• Will steel float in water?
• Are you sure – can a paper clip float
in water?
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Surface Tension
• Inward force or pull that
tends to minimize the surface
area of a liquid
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Surfactant
• Any substance which interferes
with hydrogen bonding…
• …thereby reducing surface tension
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Vapor Pressure in Water
• Would you expect water to have a
high or low vapor pressure?
• What would cause water’s vapor
pressure to be so low?
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Water in the Solid State
• What is unique about ice?
• Water is one of the few substances
that as a solid will float in its own
liquid.
• What might be cause of this?
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The Density of Water as it Freezes
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Liquid H2O
Solid H2O
Contrast in Density of Water and Ice
Hydrogen Bonding and Ice
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Water and Ice
• The fact that ice floats is critical to
many forms of life – why is this?
• The heat required to melt 1.0 gram of
water is 334 joules – the same amount
of energy required to heat 1.0 gram of
water by 80 degrees celsius!
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15.2 -- Homogeneous Aqueous
Systems
Essential Question:
How would you describe the solution
process and what are the necessary
characteristics of a solution which
conducts electricity?
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15.2 Key Concepts
• Solvent vs Solute
• Describe solution process
• Why are ionic compounds
electrolytes?
• Write formula for a hydrate
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Solvents and Solutes
• A solvent dissolves the solute – when
sugar is stirred into water, which is the
solute and which is the solvent?
• Solvents and solutes may be solids,
liquids or gases.
• How would you describe the solution
process?
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The Solution Process
• Describing Solvation -- I need
volunteers!
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Solvation
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Electrolytes
• Electrolytes
• Non-Electrolytes
• Strong Electrolytes
• Weak Electrolytes
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Electrolytes vs Non-electrolytes
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Hydrates
Copper(II) Sulfate Pentahydrate
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Common Hydrates
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Vocabulary
• Efflorescent Hydrates – Hydrates that
lose their waters of hydration when their vapor
pressure is higher than the partial pressure of
water in the air.
• Hygroscopic Hydrates – Hydrates that
remove water from the air because their vapor
pressure is lower than that of water in the air.
• Deliquescent – substances which remove
enough moisture to become wet and go into
solution
.
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15.3 -- Heterogeneous Aqueous
Systems
Essential Question:
What are the differences between a
solution, a suspension and a colloid?
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Suspensions
• The particles of a suspension are much
larger than those in a solution and they
do not stay suspended indefinitely.
• A suspension is a mixture from which
particles settle out upon standing.
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Colloids
• A heterogeneous mixture with particles
ranging in size from 1 nm to 1000 nm.
• The dispersion medium can be a solid,
liquid or gas.
• The particles are larger than those in
solutions and smaller than in those in
suspension.
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The Tyndall Effect – the scattering
of visible light by colloidal particles
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Vocabulary
• Brownian Motion – Flashes of light, or
scintillations, are seen when colloids are
studied under a microscope.
• Coagulation – clumping together of
colloidal particles causing them to
precipitate out of solution.
• Emulsions – a colloidal dispersion of a
liquid in a liquid.
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In Summary:
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