Name:_________________________________Period_____Date__________________________
Honors Chemistry I - Liquid and Solids Review
boiling point
condensation point
melting point
freezing point
London dispersion force
dipole-dipole force
hydrogen bonding
gas
liquid
solid
intermolecular force (IM)
intramolecular force
polarizable
specific heat capacity
adhesion
cohesion
viscosity
surface tension
fusion
ΔHfus
ΔHvap
Use your notes and other resources to answer the following questions:
1. What is the Kinetic-Molecular Theory? How are kinetic energy and intermolecular forces related?
Matter can exist in three states, or phases: gas, liquid, and solid. Each of these states will be described from a
molecular viewpoint in terms of four characteristics: distance between molecules, attractive forces between
molecules, the motion of molecules, and the orderliness of the arrangement of molecules.
*Kinetic energy and IMF forces determine the state of matter of a substance. The higher the kinetic energy, the
closer a substance is to a gas. The stronger the forces, the closer a substance is to a solid.
2. What are the two ways in which the phases of a substance can be changed and describe what happens in the change?
-Two ways to change the phase of a substance is changing the temperature and changing the pressure.
-Heating and cooling can change the kinetic energy of the particles in a substance
-Increasing the pressure on a substance forces the molecules closer together, which increases the strength of
intermolecular forces
3. What are three different types of intermolecular forces of attraction and rank them from strongest to weakest.
London dispersion forces Dipole-Dipole interaction Hydrogen bonding
Weakest

Strong

Strongest
Low MP or BP

High MP or BP
4. In which phase of matter (solid, liquid, gas) are intermolecular forces strongest?
In which phase Weakest?
-Hydrogen-bonding has the strongest intermolecular force.
-London dispersion forces have the weakest intermolecular forces.
*Gases have weaker forces, solids have stronger forces.
5. Which are stronger, intermolecular forces or intramolecular forces and why?
-Intermolecular forces are the attraction that occurs between molecules and are weak compared to
intramolecular forces
-Intramolecular forces are the bonds that occur within molecules and are very strong because electrons have
been shared or transferred.
6. Describe, on a molecular level, what happens when an ice cold can/bottle is placed on a wooden table on a hot, humid
day?
Water molecules are always in the air, especially on humid days. When these water molecules strike the ice-cold
can/bottle, the can/glass is very cold; the water molecules give off a lot of their energy to the less energetic
molecules of the can/bottle. The energy loss is so great for gas molecules that they turn directly into water
droplets.
7. Why does temperature remain constant when a substance melts and when a substance boils.
-As the ice begins melting, additional input of heat energy does not raise the temperature of the water, rather it
is used to overcome the intermolecular attraction during the phase change from solid to liquid.
-As the liquid begins to boil, additional input of heat energy does not raise the temperature of the water, rather it
is used to overcome the strong intermolecular attractions during the phase change from liquid to gas
8. Qualitatively compare the densities of liquid water and ice and explain what makes water unusual in this regard.
When cooled to a solid the water molecules organize into an arrangement which maximizes the attractive
interactions of the hydrogen bonds. This arrangement of molecules has greater volume (is less dense) than
liquid water (which is more dense), thus water expands when frozen.
9. The freezing point and the melting point for table sugar (sucrose) 185oC, why are both temperatures the same?
Melting point and freezing point are not the same thing; melting point is the temperature at which the substance
will go from the solid phase to the liquid phase and freezing point is the temperature at which the substance will
go from the liquid phase to the solid phase. The temperature at which these happen are the same.
Liquids & Solids Review
10. List differences between gases, liquids, and solids.
Gases,
Liquids,
High KE/low IMF
mod KE/mod IMF
Occupies vol, occupies shape
Takes on own shape and vol,
Transparent,
translucent,
low density,
mod. density,
Solids
low KE/high IMF
Shape but not volume
usually opaque
high density
11. Discuss the Physical changes of states of matter.
solids----> liq ----> gases; Melt, evaporate
Gas ----> liq ----> solid; Condense, freeze
12. Define each of the following: hydrogen bonding, dipole-dipole, and London dispersion forces
-Hydrogen bonding is a special case of dipole-dipole. Only occurs when Hydrogen is bonded to N, O, F.
-Molecules that Hydrogen bond also have dipole-dipole and London forces
-A dipole-dipole force is the attraction that exists between polar molecules in which the partial positive
charge of one polar molecule is attracted to the partial negative charge of another polar molecule
-London forces depend upon particle size and particle shape. Larger the particle and the larger the shape
the greater the London forces. In the end, London forces come down to the number of electrons (i.e. the
Molecular Mass).
-All substances have London forces involved. Non-polar molecules have only London forces
13. Discuss the relationship between intermolecular forces and freezing point (FP)
-Ice expands when freezing (contrary to matter without Hydrogen bonding) due to Hydrogen bonding.
-The weaker the IM forces the lower the FP (and MP) due to the inability to attract other molecules close
enough to become liquid.
14. Identify the relationship between intermolecular forces and boiling point (BP)
The stronger the IM forces the higher the BP due to the higher energy needed to overcome strong IM
forces in dipoles and H-bonding molecules.
15. Define and discuss the property of viscosity of liquids
Viscosity increases with increasing intermolecular forces
16. Define and discuss the property of surface tension as it applies to cohesive and adhesive forces forming a meniscus.
-Surface tension is the energy required to expand the surface area of a liquid by a unit amount.
-Substances with strong cohesive forces have a relatively strong surface tension.
-Substances with strong adhesive forces have a relatively weak surface tension.
17. Define the relationship between cohesive and adhesive forces and shape of meniscus on a liquid surface
-If cohesive IM are greater than the adhesive forces of the container surface then a convex surface
occurs forming a reverse meniscus as with mercury
-If the adhesive forces are greater than the cohesive forces then a concave surface results forming a
meniscus as with water.
18. Define the Heat of fusion of a liquid (endo)
Heat of Fusion- Energy required to convert a quantity of solid to the liquid state at the melting point
temperature.
Solid + Energy -----> Liquid
19. Define Heat of vaporization of a liquid (endo)
Heat of Vaporization- The energy required to convert a quantity of Liquid to the gaseous state at the
boiling point temperature.
Liquid + Energy -----> Gas
20. Define the reverse processes for ΔHfus and ΔHvap (exo)
Freezing is the reverse of melting(fusion)
Condensation is the reverse of boiling
Δ H of fusion = - Δ H freezing
Δ H of vaporization = - Δ H of condensation
Liquids & Solids Review
21. Determine the type of intermolecular forces acting upon each of these molecules as they go from a vapor to a liquid:
Draw Lewis Structures then tell me the types of bonds, the shapes, the polarity and the intermolecular forces.
a. HCF3
b. PCl3
H
|
F—C—F
Lewis
Structure
c. SO3
d. CH3OH
Cl
O
H
|
||
Cl—P—Cl
O—S—O
|
H—C—O—H
|
|
F
H
Bonds
_polar_covalent_
_polar_covalent_
_polar_covalent_
_polar_covalent_
Shape
__tetrahedral____
__pyramidal____
_trigonal planar_
tetrahedral & bent
Molecular
Polarity
____ Polar______
____ Polar______
__Non-Polar___
____ Polar______
Intermolecular
Forces
_London forces_
__dipole-dipole__
__London forces_
__dipole-dipole__
__London forces_
__London forces__
dipole-dipole, H-Bond_
22. For each of the following pairs of molecules, determine which has the higher boiling point and state your
reason for making this choice: (Draw them out to be sure)
a.
b.
CH2O
or
NH3
NH3 is capable of Hydrogen-Bonding while CH2O has only dipole-dipole forces
O
H
||
|
H—C—H
H—N—H
CH3Br
CH3Cl
H
or
H
|
|
H—C—Br
H—C—Cl
|
|
H
H
Cl to C bond in CH3Cl has a greater electronegativity difference than
Br to C in CH3Br resulting in a stronger partial negative charge for CH3Cl.
c.
SiO2
O═Si═O
or
CO2
Both are non-polar molecules but SiO2 has a greater Molar Mass (more e-)
making SiO2 more polarizable (stronger London forces)
O═C═O
23. Use the following information to calculate the amount of energy in joules when 45.0 grams of solid acetic acid is taken
from a temperature of 3.20oC to 190.9oC
Specific heat of solid acetic acid = 1.03 J/goC
melting point = 16.6oC
Heat of fusion - acetic acid = 192.1 J/g
Specific heat of liquid acetic acid = 2.05 J/goC
boiling point = 117.9oC
Heat of vaporization - acetic acid = 2504 J/g
Specific heat of vapor acetic acid = 1.01 J/goC
Solid: (45.0 g)(1.03J/gC)(13.4C) = 621.09 J
Melting: (192.1 J/g)(45.0 g) = 8644.5 J
Total:
Liquid: (45.0g)(2.05J/gC)(101.3C) = 9344.925 J
135000J
Boiling: (45.0g)(2504J/g) = 112680 J
Gas: (45.0g)(1.01J/gC)(73.0C) = 3317.85 J
24. Calculate the amount of heat needed to completely convert 50.0 g of ice at 0.00 ºC to steam at 100.0 ºC.
specific heat of ice - 2.09J/goC
heat of fusion - 334J/g
Melting pt of water = 0oC
specific heat of water - 4.184J/goC
heat of vaporization- 2260J/g
Boiling pt of water = 100.00C
specific heat of steam - 2.01J/goC
Melting: (50.0g)(334J/g) = 16700 J
Liquid: (50.0g)(100C)(4.18J/gC) = 20900 J
Boiling: (50.0g)(2260J/g) = 113000 J
Total: 151000 J