Chapter 17: Water and Aqueous
Systems
Ms. Knick
HAHS
CHEM 1B
Chapter 17 Section 1
Liquid Water and Its Properties:
-it is foundation of all life
-makes up 70% of body of humans
-can exist in all three phases
-Water is polar
-bonding e- shared unequally
*caused by electronegativity diff.
-Many properties of water are due to hydrogen
bonding
-water has strong attractions between the
hydrogen atoms and oxygen atoms of different
water molecules and it is very
difficult to break these bonds
Properties Resulting From H-Bonding
1) high surface tension
2) Low Vapor Pressure
3) high heat of vaporization
4) high boiling point
Surface Properties
-surface of water acts as a skin
--this is explained by surface tension:
-inward force or pull that tends to
minimize the surface area of a liquid
-holds water in shape of sphere
-can be reduced by adding a surfactant: interferes
with hydrogen bonding
ex- soap
Low Vapor Pressure
vapor pressure- pressure right above the surface
of a liquid, caused by molecules escaping to
gas phase
-b/c of H-bonding the molecules cannot escape
as easily so vapor pressure is low
-if not lakes, ponds, oceans would easily
evaporate
Chapter 17 Section 2
• -Water has a high heat of vaporization
-this is the amount of energy needed to
convert 1g of a liquid to gas at the
boiling pt.
• -difficult to break bonds to vaporize water due to THE STRONG HBONDS.
• Because of hydrogen bonding, the heat of vaporization is higher
than most other substances.
• Iron’s heat of vaporization is only 0.447, which means for the same
increase in temp as water, Fe only need 0.447 units of energy.
• Water’s high heat of vaporization (4.184) helps to moderate daily
air temperature around large bodies of water
-opposite of vap. is known as the heat of condensation (g→ℓ)
-boiling point of water is high b/c of H- bonding
-it takes more heat to disrupt molecules
*Read page 480 and write a few sentences
describing ice- solid water
Chapter 17 Section 3
aqueous solution- water sample containing
dissolved substances
solvent- dissolving medium, what does the
dissolving
*water is known as the universal solvent
solute- what is being dissolved
ex- water and ice tea mix
solutions are homogeneous mixtures-the same throughout, uniform in
composition, cannot pick out
individual pieces
-solute particles in a solution are small→ ≈1nm
solvation- process that occurs when a solute
dissolves, solute particles become surrounded
by solvent
-some substances are insoluble- not able to be
dissolved
-this is b/c their attractions are stronger
than water
-Why does oil not dissolve in water?
-because polar molecules only dissolve other
polar molecules, nonpolar only dissolve
nonpolar
-“like dissolves like”
electrolyte- conducts an electric current in
aqueous solution or the molten state
-ionic compounds are electrolytes
weak electrolyte- when in solution only a
fraction of the solute exists as ions
strong electrolyte- when dissolved almost all of
the solute exists as separate ions
nonelectrolyte- do not conduct an electric
current in aqueous or molten state
hygroscopic- salts and other
compounds that remove moisture
from the air
desiccant- hygroscopic substances
used as drying agents
ex- packets found in shoe boxes, beef
jerky
-some compounds are so hygroscopic
that they become wet when exposed
to moist air
deliquescent compounds- remove
water from air to dissolve
completely and form solutions
ex- NaOH