Slide 1 ___________________________________ 13 Properties of Liquids
___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Liquid water provides the basis for our bodies as well as
recreational sports like windsurfing.
Foundations of College Chemistry, 14th Ed.
___________________________________ Morris Hein and Susan Arena
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ Chapter Outline
2 ___________________________________ 13.1 States of Matter: A Review
13.2 Properties of Liquids
___________________________________ A. Evaporation
B. Vapor Pressure
___________________________________ C. Surface Tension
13.3 Boiling Point and Melting Point
___________________________________ 13.4 Changes of State
___________________________________ 13.5 Intermolecular Forces
13.6 Hydrates
___________________________________ 13.7 Water, a Unique Liquid
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 3 ___________________________________ States of Matter: A Review
___________________________________ Gases: contain particles that are far apart,
in random motion, and independent of one another.
___________________________________ Little contact
No attractive forces
Random motion
___________________________________ Solids: contain particles very close in space and
maintain a rigid shape. Significant attractive forces
exist between particles.
___________________________________ ___________________________________ Close contact
Strong attractive forces
Rigid shape
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___________________________________ Slide 4 ___________________________________ States of Matter: A Review
___________________________________ Liquids: intermediate between gases and solids.
Contain particles close to one another but have
fluidity (can assume the shape of a container).
___________________________________ Significant attractive forces exist between
particles in a liquid.
___________________________________ ___________________________________ Close contact
Some attractive forces
Fluid shape
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Slide ___________________________________ Evaporation
5 ___________________________________ Evaporation or Vaporization:
Escape of molecules from the liquid to the gas phase.
Liquid
___________________________________ Vapor
___________________________________ Molecules in the liquid state have
different kinetic energies (KEs).
___________________________________ Those with higher KEs can overcome
attractive forces between particles
and escape to the gas phase.
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Slide ___________________________________ Sublimation
6 ___________________________________ Phase change from the solid to gas phase that
bypasses the liquid state.
Solid
___________________________________ Vapor
___________________________________ Examples
CO2 (s)
I2 (s)
___________________________________ CO2 (g)
___________________________________ I2 (g)
___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 7 ___________________________________ Vapor Pressure
___________________________________ Molecules from the liquid phase can escape to
the vapor phase through evaporation.
Molecules in the gas phase can strike the surface
of the liquid and return to the liquid phase.
___________________________________ ___________________________________ This process is called condensation.
___________________________________ In a closed container, an equilibrium develops
between molecules evaporating and condensing.
liquid
evaporation
condensation
vapor
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 8 ___________________________________ ___________________________________ ___________________________________ Vapor Pressure
___________________________________ Vapor pressure: pressure exerted by a vapor
in equilibrium with its liquid phase.
___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 9 ___________________________________ Vapor Pressure
___________________________________ Vapor pressure: pressure exerted by a vapor
in equilibrium with its liquid phase.
___________________________________ Independent of the quantity of liquid or its surface area.
Increases with increasing temperature.
___________________________________ Depends on the strength of attraction between
molecules in the liquid state.
___________________________________ Volatile liquids: very weak attractive forces
between molecules. Evaporate very rapidly at ambient
temperature. Have high vapor pressures as a result.
© 2014 John Wiley & Sons, Inc. All rights reserved.
___________________________________ ___________________________________ Slide 10 ___________________________________ Vapor Pressure
___________________________________ Measuring Vapor Pressure of a Liquid
___________________________________ Measure using a barometer.
___________________________________ Vapor from the liquid exerts a
force on the Hg and pushes the
column downward.
___________________________________ The difference in height relative to
vacuum provides the vapor
pressure for the liquid.
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Slide 11 ___________________________________ Surface Tension
Resistance of a liquid to an increase in surface area.
___________________________________ Molecules on a liquid surface are strongly attracted
by molecules within the liquid.
___________________________________ Surface tension increases with increasing attractive
interactions between molecules.
___________________________________ ___________________________________ ___________________________________ Mercury droplets form spheres
due to surface tension.
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Slide 12 ___________________________________ ___________________________________ Capillary Action
___________________________________ Spontaneous rise of a liquid in a narrow tube.
___________________________________ Cohesive forces exist between water molecules in a liquid.
___________________________________ Adhesive forces exist between water molecules
and the walls of the container.
___________________________________ When the cohesive forces between molecules are less
than the adhesive forces between liquid and container,
the liquid will move up the walls of the container.
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___________________________________ ___________________________________ Slide ___________________________________ Capillary Action
13 ___________________________________ Capillary Action in Action
Shape of the meniscus reflects the relative strength
of cohesive forces within the liquid and adhesive
forces between the liquid and the tube.
___________________________________ ___________________________________ If convex:
adhesive forces < cohesive forces
___________________________________ If concave:
adhesive forces > cohesive forces
Hg
___________________________________ H2O
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 14 ___________________________________ ___________________________________ Boiling Point
___________________________________ Temperature at which the vapor pressure of a liquid
is equal to the external pressure above the liquid.
___________________________________ ___________________________________ Where is the boiling point of a liquid higher,
at or above sea level?
___________________________________ At sea level. The atmospheric pressure is higher.
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Slide 15 ___________________________________ Boiling Point
___________________________________ Normal boiling point:
temperature when the vapor pressure is 1 atm
___________________________________ Vapor Pressure Curve
___________________________________ Normal boiling points:
Water: 100 ºC
Ether: 35 ºC
Ethyl Alcohol: 78 ºC
___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ Boiling Point Practice
16 ___________________________________ The vapor pressure curve for water is given below.
What is the boiling point of water at 300 mmHg?
___________________________________ ___________________________________ a. 100 ºC
b. 86 ºC
___________________________________ c. 76 ºC
d. 30 ºC
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Slide 17 ___________________________________ Freezing Point or Melting Point
___________________________________ Freezing/melting point: the temperature at which the
solid phase of a substance is in equilibrium
with its liquid phase.
melting
solid
freezing
___________________________________ ___________________________________ liquid
___________________________________ While both phases are present,
the temperature remains constant.
The energy is used to change the solid to the liquid phase.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 18 ___________________________________ ___________________________________ ___________________________________ Changes of State
Heat of fusion: energy required to change 1 g
of a solid at its melting point to a liquid.
Heat of
vaporization
___________________________________ Boiling
___________________________________ ___________________________________ ___________________________________ Melting
Heat of fusion
___________________________________ Heat of vaporization: energy required to change 1 g
of a liquid to vapor at its normal boiling point.
© 2014 John Wiley & Sons, Inc. All rights reserved.
___________________________________ Slide ___________________________________ Energy and Phase Changes
19 ___________________________________ Heat of fusion: energy required to change 1 g
of a solid at its melting point to a liquid.
___________________________________ The heat of fusion for water is 335 J/g. Calculate
the amount of heat needed to melt 25.0 g of water.
___________________________________ ___________________________________ Use the heat of fusion as a conversion factor!
25.0 g
×
335 J
1g
___________________________________ = 8380 J
___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ Energy and Phase Changes
20 ___________________________________ Heat of vaporization: energy required to change 1 g
of a liquid to vapor at its normal boiling point.
___________________________________ The heat of vaporization for water is 2259 J/g.
Calculate the amount of heat needed to vaporize
25.0 g of water at 100 ºC.
___________________________________ ___________________________________ Use the heat of vaporization as a conversion factor!
25.0 g
×
2259 J
1g
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ = 56,500 J
___________________________________ ___________________________________ Phase Change Practice
21 Calculate the energy needed to convert 25.0 g
of ice at 0 ºC to steam at 100 ºC?
___________________________________ Given: heat of fusion = 335 J/g
heat of vaporization = 2259 J/g
specific heat of liquid water = 4.184 J/gºC
___________________________________ The conversion of ice to steam is a three step process:
___________________________________ 1. ice melts (total energy = mass x heat of fusion)
2. liquid water is warmed from 0° to 100°C (energy = mass x specific heat x ΔT)
3. water evaporates (energy = mass x heat of vaporization)
___________________________________ ___________________________________ Plan
The overall energy required for the process
is the sum of the 3 steps.
© 2014 John Wiley & Sons, Inc. All rights reserved.
___________________________________ Slide ___________________________________ Phase Change Practice
22 ___________________________________ Calculate the energy needed to convert 25.0 g
of ice at 0 ºC to steam at 100 ºC?
___________________________________ Calculate
1. ice melts
25.0 g ×
335 J
1g
= 8375 J
2. warm water
25.0 g ×
4.184 J
1 g ºC
× 100 ºC
3. evaporate water
2259 J
25.0 g ×
1g
Total energy required:
___________________________________ = 10,460 J
___________________________________ ___________________________________ = 56,475 J
___________________________________ E = Step 1 + Step 2 + Step 3 = 8375 J + 10,460 J + 56475 J = 75,300 J
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ Phase Change Practice
23 How many joules of energy are needed to change
10.0 g of ice at 0.00 ºC to water at 20.0 ºC?
Given: heat of fusion = 335 J/g
specific heat of liquid water = 4.184 J/gºC
___________________________________ a. 4.19 x 103 J
___________________________________ ___________________________________ b. 478 J
c. 3.35 x 103 J
___________________________________ d. 2.51 x 103 J
Plan
The conversion of ice to liquid water is a two step process.
___________________________________ 1. ice melts (total energy = mass x heat of fusion)
2. liquid water is warmed from 0° to 20 °C (energy = mass x specific heat x ΔT)
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ ___________________________________ Phase Change Practice
24 ___________________________________ How many joules of energy are needed to change
10.0 g of ice at 0.00 ºC to water at 20.0 ºC?
___________________________________ Calculate
1. ice melts
2. warm water
10.0 g
10.0 g
335 J
×
1g
×
4.184 J
1 g ºC
___________________________________ = 3350 J
___________________________________ × 20 ºC
= 837 J
___________________________________ Total energy required:
___________________________________ Energy = Step 1 + Step 2 = 3350 J + 837 J = 4.19 x 103 J
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ Intermolecular Forces
25 ___________________________________ Attractive forces between molecules.
These forces allow for formation of liquids and solids.
___________________________________ The degree of intermolecular forces correlates
with a compound’s physical properties.
___________________________________ ___________________________________ Example:
___________________________________ The stronger the interaction between molecules in a liquid,
the higher the boiling point and the lower
the vapor pressure.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 26 ___________________________________ ___________________________________ Types of Intermolecular Forces
___________________________________ Dipole-Dipole Attractions
In covalent molecules, due to different atoms having
different electronegativities, molecules are polar.
___________________________________ When polar molecules are put together,
they will align to permit interaction between
oppositely polarized portions of the molecules.
___________________________________ ___________________________________ The interaction of two polar
H2O molecules.
___________________________________ These interactions between dipoles in different molecules
are called dipole-dipole forces.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 27 ___________________________________ ___________________________________ The Hydrogen Bond
___________________________________ ___________________________________ ___________________________________ Water has very high melting and boiling points,
and heats of fusion and vaporization.
___________________________________ These anomalous properties are due to strong attraction
between water molecules due to hydrogen bonding,
a special type of dipole-dipole attraction.
___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
___________________________________ Slide 28 ___________________________________ The Hydrogen Bond
___________________________________ Hydrogen bonds: one type of strong intermolecular
force/attraction between molecules.
___________________________________ Hydrogen bonds are much weaker than ionic or
covalent bonds which are intramolecular forces.
___________________________________ ___________________________________ ___________________________________ ___________________________________ Hydrogen Bonding between H2O molecules.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 29 ___________________________________ The Hydrogen Bond
___________________________________ To form hydrogen bonds, a compound must have
covalent bonds between hydrogen and F, O or N
(a very electronegative element).
___________________________________ ___________________________________ ___________________________________ Can hydrogen bond.
Cannot hydrogen bond.
(No H attached to oxygen).
___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 30 ___________________________________ The Hydrogen Bond Practice
___________________________________ Which of the following molecules would be expected
to participate in hydrogen bonding?
___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ London Dispersion Forces
31 ___________________________________ Molecules without dipoles can also interact
with one another.
___________________________________ These interactions between nonpolar molecules and
noble gases are called London dispersion forces.
___________________________________ London forces arise from uneven, instantaneous
charge distributions due to electron movement
in nonpolar molecules.
___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ London Dispersion Forces
32 ___________________________________ This instantaneous dipole can then induce a dipole in a
neighboring nonpolar molecule, resulting in a small
attraction between particles.
___________________________________ ___________________________________ London forces are very weak forces.
___________________________________ Generally become more important as the size of the
molecule increases. Larger sizes provide more
possible electrons to provide dipoles.
___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ London Dispersion Forces
33 ___________________________________ Which of the following molecules would have the
largest London dispersion forces?
___________________________________ ___________________________________ a. CH4
b. C4H10
c. C15H32
d. C8H18
The largest hydrocarbon
(i.e., having the largest molar mass)
will have the strongest London forces.
___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ Hydrates
34 ___________________________________ Hydrates are solids that contain water molecules as
part of their crystalline structure.
___________________________________ The formula lists the anhydrous (without water)
formula of the compound. The number of waters present
per structural unit (water of hydration) are then given.
___________________________________ CaCl2·2H2O
___________________________________ Hydrates are named by placing a prefix corresponding
to the number of water molecules, followed by hydrate
___________________________________ CaCl2·2H2O
FeCl3·6H2O
calcium chloride dihydrate
iron(III) chloride hexahydrate
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ ___________________________________ Hydrates
35 ___________________________________ Hydrates will often decompose by
losing water upon heating.
CuSO4·5 H2O (s)
250°C
___________________________________ CuSO4 (s) + 5 H2O (g)
___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ Hydrates Practice
36 ___________________________________ Calculate the percent water in Epsom salts
MgSO4·7H2O (s).
___________________________________ 1. Calculate the molar mass of the compound.
___________________________________ Molar Mass MgSO4·7H2O (s) = 120.4 + 7(18.02) = 246.5 g
___________________________________ 2. Calculate the % water of the compound.
% water =
Mass water
x 100 =
Molar mass
126.1 g
246.5 g
x 100 = 51.16 %
___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide ___________________________________ Hydrates Practice
37 ___________________________________ What is the percent water in CuSO4·5H2O (s)?
___________________________________ a. 56.46%
1. Calculate the molar mass of the compound.
b. 36.08%
c. 63.92%
Molar Mass CuSO4·5H2O (s)
= 159.6 + 5(18.02) = 249.2 g
d. 61.57%
2. Calculate the % water of the compound.
% water =
Mass water
x 100 =
Molar mass
90.10 g
259.2 g
___________________________________ ___________________________________ ___________________________________ x 100 = 36.08 %
___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 38 ___________________________________ Water: A Unique Liquid
___________________________________ Water covers 75% of the Earth’s surface;
97% of all water resides in the oceans.
___________________________________ Water constitutes 70% of a human body by mass.
___________________________________ Physical Properties of Water
Colorless, odorless, tasteless liquid.
___________________________________ More dense in liquid than solid phase (why ice floats).
___________________________________ High boiling point, high heat of fusion/vaporization
due to hydrogen bonding.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 39 ___________________________________ ___________________________________ Water: A Unique Liquid
___________________________________ Structure of Water Molecules
Two OH bonds are formed by the overlap of 1s orbitals
on H with orbitals on the O.
___________________________________ The molecular geometry of water is
bent, due to the two lone pairs on
oxygen.
___________________________________ ___________________________________ Water has a permanent dipole due to
the molecules’ shape and the polar
O-H bonds.
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Slide 40 ___________________________________ Water: A Unique Liquid
___________________________________ Sources of Water for Human Consumption
Climate change and increased demand for fresh water
make finding and sustaining sources of potable
water critical for future generations.
Strategies to Sustain Water Supplies
1. Reclamation of wastewater
Currently used in agriculture and industry
2. Desalination of seawater
Expensive, but useful for countries near the ocean.
3. Low temperature distillation
At low pressure, water’s boiling point is reduced.
Less energy is required to separate the salts by boiling.
4. Combustion of H2
H2 and O2 react very exothermically to produce water.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 41 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Chemistry in Action: Osmosis
___________________________________ Osmosis: process by which water flows through a
membrane from a region of more pure water
to a region of less pure water.
___________________________________ ___________________________________ ___________________________________ ___________________________________ Water flows into the raisin to dilute the sugar.
The size of the raisin expands.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 42 ___________________________________ ___________________________________ Chemistry in Action: Reverse Osmosis
___________________________________ Reverse Osmosis: process by which water flows through
a membrane from a region of less pure water to a region
of more pure water, due to the presence of an external
stimulus (typically pressure)
___________________________________ ___________________________________ ___________________________________ Process often used in water purification.
A semipermeable membrane is used and
only water can pass through.
By applying pressure, only water passes through
the membrane. The water is now pure!
© 2014 John Wiley & Sons, Inc. All rights reserved.
___________________________________ ___________________________________ Slide 43 ___________________________________ Learning Objectives
___________________________________ 13.1 States of Matter: A Review
___________________________________ Review the states of matter and their properties.
13.2 Properties of Liquids
___________________________________ Explain why liquids tend to form drops and the process
of evaporation and its relationship to vapor pressure.
___________________________________ 13.3 Boiling Point and Melting Point
___________________________________ Define boiling and melting points and determine
the boiling point of a liquid from a graph of
temperature and vapor pressure.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Slide 44 ___________________________________ ___________________________________ Learning Objectives
___________________________________ 13.4 Changes of State
Calculate the amount of energy involved
in a change of state.
___________________________________ 13.5 Intermolecular Forces
Describe the three types of intermolecular forces
and explain their significance in liquids.
___________________________________ 13.6 Hydrates
___________________________________ Explain what hydrates are, write formulas for hydrates
and calculate the percent water in a hydrate.
___________________________________ 13.7 Water, A Unique Liquid
Describe the characteristics of water in terms of its
structure and list the sources of drinking water.
© 2014 John Wiley & Sons, Inc. All rights reserved.
___________________________________