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Chapter 12
Liquids, Solids, and Intermolecular Forces

12-01
Title
Gas, liquid, and solid states
Caption
The depiction of molecules in each physical state gives us some insight into the properties of each state: Gases take on the shape of the container and completely fill it; liquids take on the shape of the container, but do not completely fill it; solids assume their own shape independent of the container.
Notes
The picture also shows the relative order and spacing of molecules in each state: Gases are randomly ordered, with much space between molecules; liquids have no long range order, and there is little space between molecules. Solids have long-range order, with little space between molecules.
Keywords
solid, liquid, gas, physical state
12-02
Title
Water molecules in an Erlenmeyer flask
Caption
Since water molecules in liquid water are free to move around each other, they flow to assume the shape of their container.
Notes
The water molecules will be in motion, and there will be a significant attraction between the molecules, because of water's polarity.
Keywords
solid, physical state
12-05
Title
Molecular interaction on surface of water and interior
Caption
Molecules at the surface of a liquid have fewer neighbors with which to interact. How does this affect the surface of a liquid?
Notes
The greater the attraction between the molecules, the more the molecules "cling" to one another. The result is the observable effect of surface tension. However, the surface molecules have fewer neighbors, so their attraction to other molecules is less. These molecules may be able to escape from the liquid, provided they find enough energy.
Keywords
solid, physical state, intermolecular attraction, surface tension
12-11
Title
Molecules can evaporate from the surface of a liquid
Caption
Since molecules on the surface of a liquid are held less tightly than those in the interior, they can break away into the gas phase. This is called evaporation.
Notes
The greater the attraction between the molecules, the more the molecules "cling" to one another. The result is the observable effect of surface tension. However, the surface molecules have fewer neighbors, so their attraction to other molecules is less. These molecules may be able to escape from the liquid, provided they find enough energy.
Keywords
solid, physical state, intermolecular attraction, evaporation
12-14
Title
Boiling point determination for water
Caption
The temperature of water as it is heated from room temperature through boiling. During boiling, the temperature remains at 100 ¡C until all the liquid is evaporated.
Notes
The flat part of the graph represents the time during which the water boils. After all liquid water has changed to steam, the temperature begins to rise again.
Keywords
gas, boiling, temperature, liquid
12-14-01un
Title
Multistep solution map for calculating heat of vaporization
Caption
The stated factors use data from the periodic table and the formula H20 to make the conversion from mass of H20 to moles. The mass of one mole of H20 is calculated by adding the masses of hydrogen and oxygen, according to the chemical formula. The 40.6 kJ factor was obtained by experiment and published in reference tables.
Notes
The solution map allows us to calculate the mass of water that can be vaporized at 100 oC. Note that this is NOT a calculation to tell how much heat is needed to reach 100 oC. Rather, this is the heat needed to take water already at 100 oC from the liquid to the gaseous state.
Keywords
gas, boiling, temperature, liquid, heat, vaporization, kilojoule
12-14-02un
Title
Multistep solution map for using heat of vaporization in a calculation
Caption
In this example, we find the mass of water that can be vaporized by 155 kJ. The stated factors use data from the periodic table and the formula H20 to make the conversion from mass of H20 to moles. The mass of one mole of H20 is calculated by adding the masses of hydrogen and oxygen, according to the chemical formula. The 40.6 kJ factor was obtained by experiment and published in reference tables.
Notes
The solution map allows us to calculate the mass of water that can be vaporized at 100 oC. Note that this is NOT a calculation to tell how much heat is needed to reach 100 oC. Rather, this is the heat needed to take water already at 100 oC from the liquid to the gaseous state.
Keywords
gas, boiling, temperature, liquid, heat, vaporization, kilojoule
12-15
Title
The temperature of water as it is heated from ice through melting
Caption
The temperature of water as it is heated from ice through melting. During melting, the temperature remains at 0 ¡C until all the ice is melted.
Notes
The flat part of the graph represents the time during which the ice melts. After all ice has changed to liquid water, the temperature begins to rise again.
Keywords
solid, melting, temperature, liquid, ice
12-15-01un
Title
Multistep solution map for calculating heat of fusion
Caption
The stated factors use data from the periodic table and the formula H20 to make the conversion from mass of H20 to moles. The mass of one mole of H20 is calculated by adding the masses of hydrogen and oxygen, according to the chemical formula. The 6.02 kJ factor was obtained by experiment and published in reference tables.
Notes
The solution map allows us to calculate the heat required to melt a mass of ice at 0 oC. Note that this is NOT a calculation to tell how much heat is needed to reach 0 oC. Rather, this is the heat needed to take ice already at 0 oC to the liquid state.
Keywords
solid, melting, temperature, liquid, heat, fusion, kilojoule
12-15-02un
Title
Multistep solution map for using heat of fusion in a calculation
Caption
In this example, we find the mass of water that can be vaporized by a given amount of heat, in kilojoules. The stated factors use data from the periodic table and the formula H20 to make the conversion from mass of H20 to moles. The mass of one mole of H20 is calculated by adding the masses of hydrogen and oxygen, according to the chemical formula. The 6.02 kJ factor was obtained by experiment and published in reference tables.
Notes
The solution map allows us to calculate the mass of ice that can be melted at 0 oC.
Keywords
solid, melting, temperature, liquid, heat, fusion, kilojoule
12-16
Title
Instantaneous dipoles: all species have them
Caption
Random fluctuations in the electron distribution of a helium atom cause instantaneous dipoles to form. In this example, helium atoms display uneven electron distributions that give rise to instantaneous dipoles. The attraction between instantaneous dipoles is called the dispersion force.
Notes
All atoms and nonpolar molecules will exhibit the dispersion force.
Keywords
electron, dipole, dipole moment, instantaneous dipole, helium, dispersion force
12-17
Title
Helium atoms attract each other weakly
Caption
An instantaneous dipole on any one helium atom induces instantaneous dipoles on neighboring atoms. The neighboring atoms then attract one another. This attraction is called the dispersion force.
Notes
All atoms and nonpolar molecules will exhibit the dispersion force.
Keywords
electron, dipole, dipole moment, instantaneous dipole, helium, dispersion force
12-18
Title
Formaldehyde has a permanent dipole
Caption
Molecules such as formaldehyde are polar and therefore have a permanent dipole. The dipole arises from a combination of polar covalent bonds and favorable geometry.
Notes
This attraction between permanent dipoles is called the dipoleĞdipole force.
Keywords
electron, dipole, dipole moment, permanent dipole, formaldehyde, dipoleĞdipole force
12-19
Title
Formaldehyde molecules attract each other
Caption
The positive end of a polar molecule is attracted to the negative end of its neighbor. This attraction is called a dipoleĞdipole attraction.
Notes
Polar molecules will exhibit the dipoleĞdipole force.
Keywords
electron, dipole, dipole moment, permanent dipole, formaldehyde, dipoleĞdipole force
12-19-01un
Title
Comparison of formaldehyde and ethane
Caption
Despite having the same mass, ethane and formaldehyde have very different properties. Formaldehyde, with its permanent dipole, has a much higher boiling point than ethane, which has only an instantaneous dipole. The higher boiling point indicates a much stronger attraction between molecules.
Notes
Students might be challenged to find other pairs of compounds which show stronger attractions among the molecules with permanent dipoles.
Keywords
electron, dipole, dipole moment, permanent dipole, formaldehyde, dipoleĞdipole force, instantaneous dipole, ethane, dispersion force
12-19-03un
Title
CH2Cl2 is a polar molecule
Caption
The C-Cl bonds are more polar than the C-H bonds. The bonds therefore don't cancel, and the molecule is polar.
Notes
The compound will exhibit the dipoleĞdipole force.
Keywords
electron, dipole, dipole moment, permanent dipole, dipoleĞdipole force
12-21
Title
Attractive forces are responsible for DNA's structure
Caption
DNA is composed of repeating units called nucleotides. Each nucleotide is composed of a sugar, a phosphate, and a base. The famous double-helix structure of DNA is due to hydrogen bonding between the nucleotides.
Notes
Hydrogen bonding is an unusually powerful dipoleĞdipole attractive force.
Keywords
DNA, hydrogen bonding, nucleotide, sugar, phosphate, base
12-22
Title
Base pairs are held together by hydrogen bonding
Caption
The two halves of the DNA double helix are held together by hydrogen bonds.
Notes
Hydrogen bonding is an unusually powerful dipoleĞdipole attractive force. However, hydrogen bonds are much weaker than covalent bonds.
Keywords
DNA, hydrogen bonding, nucleotide, sugar, phosphate, base
12-23
Title
Hydrogen fluoride exhibits hydrogen bonding
Caption
In HF, the hydrogen on one molecule is strongly attracted to the fluorine on its neighbors. This attraction is called a hydrogen bond.
Notes
Hydrogen bonding is an unusually powerful dipoleĞdipole attractive force. However, hydrogen bonds are much weaker than covalent bonds.
Keywords
hydrogen bonding, dipole, polar, hydrogen, fluorine, hydrogen fluoride
12-23-01un
Title
Comparison of methanol and ethane
Caption
Despite having nearly the same mass, ethane and methanol have very different properties. Methanol, with its hydrogen bonding, has a much higher boiling point than ethane, which has only an instantaneous dipole. The higher boiling point indicates a much stronger attraction between molecules.
Notes
Students might be challenged to find other pairs of compounds which show stronger attractions among the molecules with hydrogen bonding.
Keywords
electron, dipole, dipole moment, permanent dipole, methanol, hydrogen bonding, instantaneous dipole, ethane, dispersion force
12-23-02un
Title
Predicting physical state from the attractive force
Caption
Which molecule is a liquid at room temperature, and why?
Notes
Formaldehyde has dipoleĞdipole attractions; fluoromethane has dipoleĞdipole attractions, but hydrogen peroxide has hydrogen bonding. The hydrogen bonding has the strongest force; it will be the liquid.
Keywords
dipole, dipole moment, permanent dipole, hydrogen bonding, instantaneous dipole, dispersion force, dipoleĞdipole force
12-23-03d
Title
Hydrogens exhibit very weak attractions
Caption
Random fluctuations in the electron distribution of a hydrogen molecule cause instantaneous dipoles to form. In this example, hydrogen molecules display uneven electron distributions that give rise to instantaneous dipoles. The attraction between instantaneous dipoles is called the dispersion force.
Notes
The hydrogens are very weakly attracted; the boiling point will be low. All atoms and nonpolar molecules will exhibit the dispersion force.
Keywords
electron, dipole, dipole moment, instantaneous dipole, hydrogen, dispersion force
12-23-04e
Title
Hydrogen chloride molecules exhibit strong attractions
Caption
HCl has an uneven electron distribution within the molecule, giving rise to dipoleĞdipole forces.
Notes
The HCl's are strongly attracted; the boiling point will be high. All polar molecules will exhibit the dipoleĞdipole force.
Keywords
electron, dipole, dipole moment, permanent dipole, hydrogen chloride, dipoleĞdipole force
12-23-05f
Title
Hydrogen fluoride molecules exhibit very strong attractions
Caption
HF has an uneven electron distribution within the molecule, giving rise to hydrogen bonding.
Notes
The HF's are very strongly attracted; the boiling point will be very high. Molecules with H-F, H-O, or H-N bonds will exhibit hydrogen bonding.
Keywords
electron, dipole, dipole moment, permanent dipole, hydrogen fluoride, hydrogen bonding
12-24
Title
Methanol molecules attract through hydrogen bonding
Caption
Since methanol contains hydrogen atoms directly bonded to oxygen, methanol molecules form hydrogen bonds to one another. The hydrogen atom on one methanol molecule is attracted to the oxygen atom of its neighbor.
Notes
The H in methanol's O-H bond is very strongly attracted to the O in a neighboring methanol's O-H bond; the boiling point will be very high. Molecules with H-F, H-O, or H-N bonds will exhibit hydrogen bonding.
Keywords
electron, dipole, dipole moment, permanent dipole, methanol, hydrogen bonding
12-25
Title
Water molecules form strong hydrogen bonds with one another
Caption
Since water contains hydrogen atoms directly bonded to oxygen, water molecules form hydrogen bonds to one another. The hydrogen atom on one water molecule is attracted to the oxygen atom of its neighbor.
Notes
The H in water's O-H bond is very strongly attracted to the O in a neighboring water's O-H bond; the boiling point will be very high. Molecules with H-F, H-O, or H-N bonds will exhibit hydrogen bonding.
Keywords
electron, dipole, dipole moment, permanent dipole, water, hydrogen bonding
12-26
Title
Crystalline solids
Caption
Crystalline solids are divided into three categories.
Notes
Solids may also be amorphous.
Keywords
crystalline solid, solid, crystal
12-29
Title
A metal's electron sea
Caption
In the simplest model of a metal, each atom donates one or more electrons to an "electron sea." The metal then consists of the metal cations in a negatively charged electron sea.
Notes
Metals have in general too few valence electrons to satisfy octets through sharing with individual atoms, as nonmetals do. Instead, the electrons are dispersed over many atoms, resulting in the "electron sea." The electron sea promotes high electrical conductivity.
Keywords
metal, electron, cation, anion
12-30-05k
Title
Which molecule is most likely to evaporate?
Caption
The molecule with the fewest neighbors will be most likely to break free: to evaporate
Notes
The greater the attraction between the molecules, the more the molecules "cling" to one another. The result is the observable effect of surface tension. However, the surface molecules have fewer neighbors, so their attraction to other molecules is less. These molecules may be able to escape from the liquid, provided they find enough energy.
Keywords
solid, physical state, intermolecular attraction, evaporation
12-30-06l
Title
Sodium stearate: a soap
Caption
Soaps have a polar region and a nonpolar region. The polar region is located at the right of the molecule, where the oxygens and the Na+ ion are found.
Notes
The polar region can interact strongly with water; the nonpolar region interacts with grease and dirt. One might think of soap as a mediator between two otherwise immiscible substances.
Keywords
polar, nonpolar, soap, sodium, stearate, immiscible

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