Polarity and Intermolecular Forces Unit
November 2-10 (2015)
Day 1: VSEPR Lab
Objectives (SWBAT):
Physical Science 9- explain, predict, and draw VSEPR models for various covalent compounds
Evaluated by:
VSEPR Lab
Class structure:
Do Now: Draw the Lewis Dot diagram from NH4+.
1. Engage- Answer the pre-lab questions to begin thinking of structure as 3D.
2. Explore- Draw each of the Lewis structures (structural formulas) in question four then use the gumdrops
and toothpicks to model these structures in 3 dimensions.
3. Explain- Students will draw the molecular geometry of the gumdrop models they’ve made then use the
VSEPR shapes worksheet to name each of these structures.
4. Elaborate- Students will draw the Lewis structures of four additional compounds and predict their
geometries without the gumdrops. The teacher will explain the effect of lone pairs on structure.
Summary: VSEPR theory explains the shape of molecules in three dimensional space and assumes that electron pairs
repel each other as far as possible. This creates either a linear, bent, trigonal planar, tetrahedral, trigonal bipyrimidal, or
octahedral shape.
Day 2: VSEPR Lab Continued
Objectives (SWBAT):
Physical Science 9- explain, predict, and draw VSEPR models for various covalent compounds
Evaluated by:
VSEPR Lab
Class structure:
Do Now: Draw the structural formulas for the seven compounds on page three of the lab.
1. Engage- Students will use gumdrops and toothpicks to model their Lewis structures in three dimensions
then draw these in the column for molecular geometry.
2. Explore- Students will use new vocabulary (lone pairs and steric numbers) with the VSEPR shapes
worksheet to write out the electron geometry and name the 3D model.
3. Explain- Students will draw the Lewis structures of two additional compounds and predict their
geometries without the gumdrops. The students will then compare the predicted bond angles to
explain the effect of lone pairs on the structure of a compound.
4. Elaborate- Students will draw the structural and molecular geometries for more complex compounds to
complete the post-lab.
Summary: Each pair of electrons on the central atom acts as another attached atom and under VSEPR theory, all atoms
on the central atom repel to be as far away from each other as possible. This determines the 3D structure of a
compounds which in turn affects its properties.
Day 3: Polarity
Objectives (SWBAT):
Physical Science 22- predict the bond that will form between two elements based on electronic structure and
electronegativity (ionic, polar covalent, or nonpolar covalent)
Evaluated by:
Polarity of Molecules Worksheet
Class structure:
Do Now: Draw the structural and molecular formulas for CO2 and H2O.
1. Engage- Students will explain why despite both compounds in the Do Now having 2 bonded atoms,
one’s 3D geometry is linear and one is bent. The teacher will assign vocabulary to this difference
a. Polar: an asymmetrical covalent compound that has an uneven charge distribution; one section
of the compound is more negative than the rest giving the compound a partial positive side and
partial negative side.
b. Nonpolar: a symmetrical covalent compound that has even charge distribution.
2. Explore- Students will draw structural and molecular formulas for ten different compounds and use
these pictures to determine symmetry and polarity.
3. Explain- Students will pair/share answers to check their work then the teacher will explain how to
recognize whether a bond is polar or nonpolar (this is different than determining whether a compound
is polar or nonpolar). Students calculate electronegativity differences in each bond of the classwork
page and use this information to identify whether each bond is polar or nonpolar.
4. Elaborate-Students will draw the structural formulas, determine symmetry, and determine compound
polarity for the compounds on the polarity of molecules homework sheet. Students will also highlight
any polar bonds determined by electronegativity.
Summary: Covalent compounds can be classified as polar (if the compound lacks overall symmetry) or nonpolar (if the
compound is symmetric overall). Bonds can be classified as polar or nonpolar based on differences in electronegativity.
Polar covalent bonds have a difference between 0.5 and 1.9 while nonpolar covalent bonds are different by less than
0.5.
Day 4: Intermolecular Forces
Objectives (SWBAT):
Physical Science 24- Predict types of intermolecular forces present in molecules and rank these forces by strength
Physical Science 46- Describe the influence of intermolecular forces on the physical and chemical properties of covalent
compounds
Evaluated by:
IMF pre-lab
Class structure:
Do Now: Draw one polar and one nonpolar compound each with carbon as the central atom. Justify your
drawing in terms of symmetry.
1. Engage- NOTES: Intermolecular forces (IMF)
a. Ion-Ion force (electrostatic force): present between ionic compounds- the positive ion is very
strongly attracted to the negative ion and vice versa
b. Hydrogen bond: present between polar covalent compounds that contain a highly
electronegative element (N, O, F, Cl, Br, and I)- The uneven charge distribution leaves Hydrogen
with a partial positive charge and the other element with a partial negative charge. The partial
negative charge on this element is strongly attracted to the partial positive charge on the
hydrogen of a neighboring compound and vice versa.
c. Dipole-Dipole Force: present between polar covalent compounds- The uneven charge
distribution leaves one element with a partial positive charge and another element with a partial
negative charge. The partial negative charge on this element is attracted to the partial positive
charge on a neighboring compound and vice versa.
d. London Dispersion Force: present between nonpolar compounds- The even charge distribution
means that there is no partial positive or partial negative portion of the compound. Instead,
neighboring compounds are only attracted to each other when the random movement of
electrons causes one section of a molecule to be more negative than another and the same
thing happens in a neighboring compound at the same time. At this point, the compounds’
positive and negative portions are attracted to each other. This is a very weak force.
2. Explore- Students will use the classwork sheet from day 3 to practice identifying IMFs.
3. Explain- Students will pair/share their answers then, as a group, try to order these compounds from
strongest attraction to weakest attraction.
4. Elaborate- Students will complete the pre-lab for day 5’s IMF lab.
Summary: There are four types of intermolecular forces that, in order from weakest to strongest, include Dipole
interactions, London Dispersion forces, Hydrogen bonds and Ionic bonds.
Day 5: Intermolecular Forces Lab
Objectives (SWBAT):
Physical Science 24- Predict types of intermolecular forces present in molecules and rank these forces by strength
Physical Science 46- Describe the influence of intermolecular forces on the physical and chemical properties of covalent
compounds
Evaluated by:
IMF lab
Class structure:
Do Now: Get into safety compliance (goggles, aprons, sleeves, hair, and shoes) while your pre-lab is checked.
1. Engage- The class will review lab safety and buret usage. Remember these chemicals are flammable and
several have strong odors- be safe or be banned from labs.
2. Explore- Students will follow the steps at the stations around the room and record observations about
polarity, surface tension, evaporation rate, and boiling point. (approximately 8 minutes per station)
3. Explain- Students will explain their results in terms of intermolecular forces.
4. Elaborate- Students will compare their predictions to their results by answering the post-lab questions.
Summary: Covalent compounds have a lower melting point and boiling point than ionic compounds because the ionic
bond is the strongest of the four bond types. The stronger the force holding the molecule together, the higher the
melting point, higher the surface tension, and longer evaporation rate.
Day 6: Review and Tie the Lab in
Objectives (SWBAT):
Physical Science 24- Predict types of intermolecular forces present in molecules and rank these forces by strength
Physical Science 46- Describe the influence of intermolecular forces on the physical and chemical properties of covalent
compounds
Evaluated by:
IMF flipbook
Class structure:
Do Now: Which compounds, CBr4 or HBr would have a higher boiling point and why?
1. Engage- Students will compare the properties of ionic and covalent compounds then relate this to the
structure and IMFs of these compounds.
2. Explore- Students will make a flip book for each of the four intermolecular forces (ion-ion, hydrogen
bond, dipole-dipole, and London Dispersion Force) that orders the forces by strength then gives an
example, states how to recognize the force, defines the force, and describes the effect on the properties
of the compound.
3. Explain- The teacher will review the vocabulary on day 7’s test then provide each group with a set of
practice problems. The group will complete the problems then come to the board to explain their
answer to the class.
4. Elaborate- Students will continue to study the material at home for day 7’s test.
Summary: Covalent compounds are weak than ionic compounds but there are differences among covalent compounds
that stem from differences in their three dimensional structure. Unlike ionic compounds which are all held together by
strong ion-ion forces (electrostatic attraction) and have a crystalline structure. Covalent compounds share electrons and
the evenness of this sharing affects the properties. If the electrons are shared evenly (nonpolar), there is nothing
attracting one molecule to another, leading to low surface tension, quick evaporation/boiling (low boiling point and high
evaporation rate). If the electrons are shared unevenly (polar) or very unevenly (hydrogen bond), there is a partial
positive side to the compound and a partial negative side to the compound which leads to one molecule attracting
another. This attraction holds the molecules together leading to high surface tension and slow evaporation/boiling (high
boiling point and low evaporation rate).
Day 7: Test- Polarity and IMF
Objectives (SWBAT):
Physical Science 5, 9, 13, 16, 22, 23, 24, and 46- Demonstrate at least 75% proficiency over the material from this unit.
Evaluated by:
Test- Polarity and IMF
Class structure:
Do Now: Take out a calculator and something to write with, open your binder to the table of contents and place
it on the back bench, move your bags to the A/C, and clear your calculator RAM
TEST
Summary: This unit built on the last unit (Lewis Structures) and the previous unit (Periodic Table) and we will continue to
build on this information with the next unit (Naming) and every unit after that. Do not get behind or allow yourself to
let information fall to the back of your mind. If you keep reviewing this material and asking questions when you do not
understand, the class will be much easier for you as we move forward.
GLE
Objective
Day(s) Addressed
Physical
Science 9
Draw accurate valence electron configurations and Lewis dot diagrams for selected
molecules, ionic and covalent compounds, and chemical equations
1, 2, 3, 4
Physical
Science 13
Identify the number of bonds an atom can form given the number of valence
electrons
1, 2, 3, 4
Physical
Science 22
Predict the kind of bond that will form between two elements based on electronic
structure and electronegativity of the elements
3, 4
Physical
Science 23
Model chemical bond formation by using Lewis dot diagrams for ionic, polar, and
nonpolar compounds
1, 2, 3, 4
Physical
Science 24
Describe the influence of intermolecular forces on the physical and chemical
properties of covalent compounds
4, 5, 6
Physical
Science 46
Identify and compare intermolecular forces and their effects on physical and
chemical properties
4, 5, 6
Vocabulary
Structural Formula
Polar
Dipole-Dipole
Molecular Geometry
Nonpolar
London Dispersion Force
Electron Geometry
Ion-Ion Force (electrostatic)
Intermolecular Force
VSEPR Theory
Hydrogen Bond
Assessment Design- Unit 7
Basic: 6 Questions
Standard: 12 Questions
Essential Skills and Learning Objectives
Expanded: 6 Questions
Type of
Question
(MC, CR, P)
Basic
(Remember &
Understand)
Standard
(Apply &
Analyze)
Expanded
(Evaluate &
Create)
Draw accurate Lewis dot diagrams for selected molecules
1 MC
3 CR
1 CR
Model chemical bond formation of polar and nonpolar
compounds through VSEPR
2 MC
3 CR
1 MC
2 CR
Predict the kind of bond (polar, nonpolar, ionic) that will
form between two elements based on electronic structure
and electronegativity of the elements
1 MC
2 CR
1 CR
Identify and compare intermolecular forces and their
effects on physical and chemical properties
2 CR
1.5 CR
2 MC
1.5 CR
1 MC