Physical Science
Quarter 3 – Module 3:
Polar or Nonpolar?
Physical Science – Grade 11
Quarter 3 – Module 3: Polar or Nonpolar?
First Edition, 2020
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Physical Science
Quarter 3 – Module 3:
Polar or Nonpolar?
Introductory Message
For the facilitator:
As a facilitator, you are expected to orient the learners on how to use this
module. You also need to keep track of the learners' progress while allowing them to
manage their learning at home. Furthermore, you are expected to encourage and
assist the learners as they do the tasks included in the module.
For the learner:
As a learner, you must learn to become responsible for your learning. Take
time to read, understand, and perform the different activities in the module.
As you go through the different activities of this module be reminded of the
following:
1. Use the module with care. Do not put unnecessary mark/s on any part of the
module. Use a separate sheet of paper in answering the exercises.
2. Don’t forget to answer Let Us Try before moving on to the other activities.
3. Read the instructions carefully before doing each task.
4. Observe honesty and integrity in doing the tasks and checking your answers.
5. Finish the task at hand before proceeding to the next.
6. Return this module to your teacher/facilitator once you are done.
If you encounter any difficulty in answering the tasks in this module, do not
hesitate to consult your teacher or facilitator. Always bear in mind that you are not
alone. We hope that through this material, you will experience meaningful learning
and gain a deep understanding of the relevant competencies. You can do it!
ii
Let Us Learn
This module was designed for you, the learners. It is to facilitate you to learn
the appropriate knowledge and skills as you go through a series of worthwhile
activities. The lessons are arranged sequentially in this course to ease understanding
and mastery. The parameter of this module allows you to gain a concrete
understanding of polar and nonpolar molecules.
After going through this module, you are expected to:
• Determine if a molecule is polar or nonpolar given its structure (S11/12PSIIIc-15).
Let Us Try!
Choose the best answer and write this on a separate paper.
1.
What is meant when a molecule is said to be polar?
A. The molecule is symmetrical.
B. Both ends are positively charged.
C. Both ends are negatively charged.
D. One end is positively charged, and the other is negatively charged.
2.
Why is ammonia (NH3) classified as a polar molecule?
A. Each carbon-chloride bond is polar.
B. N-H bonds are non-polar.
C. Nitrogen and hydrogen are both nonmetals.
D. NH3 molecules have asymmetrical charge distributions.
3.
Which statement best explains why carbon tetrachloride (CCl 4) is nonpolar?
A. It is a gas.
B. Carbon and chlorine are both nonmetals.
C. Nitrogen and hydrogen are both nonmetals.
D. NH3 molecules have asymmetrical charge distributions.
4.
Which of the following molecular geometry shapes is most likely to be a
nonpolar molecule?
A. Linear
C. Bent
B. Tetrahedral
D. all of the above
1
5.
Based on the structure of carbon tetrachloride, which of the
following statements is TRUE?
Figure 1
Carbon Tetrachloride (CCl4)
A.
B.
C.
D.
It is polar because it is a tetrahedral molecule.
It is nonpolar because of its symmetrical structure.
It is polar due to the high electronegativity difference of C & Cl atoms.
It is nonpolar because the bonds between C & Cl atoms are nonpolar.
Let Us Study
Different substances behave in different ways. In the previous experiment, you
have observed that water and oil do not mix. This is due to the nature of water and
oil molecules. Water has polar molecules and oil is made up of nonpolar molecules.
So, how do we determine if a molecule is polar or nonpolar? Surely, we cannot
expect to try and mix up all substances we come across with, and even after that we
still would have to guess which is polar or nonpolar. To make things simple, we have
to understand the molecules that make up these substances, from this we can
analyze their molecular structures and determine if they are polar or nonpolar.
Two main factors determine the polarity of molecules. These are:
1. the polarity of the bonds between the atoms; and,
2. the geometric shape of the molecule.
Recall your lessons in junior high school science. Atoms of each element have
different properties such as atomic number, mass, oxidation number, etc. One of
these is what we call electronegativity. Electronegativity is the relative tendency of an
atom to attract electrons to itself when chemically combined with other atoms. The
higher the value of electronegativity, the more it tends to pull electrons toward itself.
The difference in electronegativity of atoms within a molecule determines the
type of bond they share. Read and analyze these comic strips below:
Atoms and Electronegativity
When atoms of approximately equal
electronegativity combine to form molecules, the
attraction (figure 2) and (most of the time)
sharing of electrons are the same (figure 3).
These molecules form nonpolar bonds.
Figure 2
2
Figure 4
Figure 3
When there is a huge difference in electronegativity, there is unequal sharing
of electrons which results in the formation of a nonpolar bond (figure 4).
In a molecule of chlorine gas (Cl2), there is equal sharing of electrons which
forms a bond between the two Cl atoms. This bond is called nonpolar covalent bond.
When there is unequal sharing of electrons, as in the case of hydrochloric acid (HCl)
in figure 5, the shared electron tends to draw closer to the more electronegative atom
which is chlorine. This bond is called polar covalent bond.
A polar bond has a slightly negative end labeled with δ- (sigma), and a slightly
positive end labeled δ+. The polarity of a bond is sometimes indicated by a simple
arrow pointing from the positive end towards the negative end of the bond (figure 6).
Figure 6
https://drgchemistry.weebly.com/uploads/2/4/8/9/248949
32/topic_3_-_polar_bonds.pdf
Figure 5
The difference of electronegativity between the atoms forming a bond can give
us an indication of the polarity of the bond. The greater the electronegativity
difference, the more polar the bond becomes.
Use the table below as a useful guide in classifying the bond in a molecule.
Table 1: Electronegativity Difference and Bond Type
Electronegativity Difference
Type of Bond
Example
Na and Cl
≥ 2.0
Ionic
/0.9 - 3.0/ = 2.1
H and Cl
0.5-1.9
Polar Covalent
/2.1 - 3.0/ = 0.9
Nonpolar
Cl and Cl
≤ 0.4
Covalent
/3.0 - 3.0/ = 0.0
Source: https://slideplayer.com/slide/2816982/
3
However, the type of bond is not the only determining factor that determines
the overall polarity of a molecule. Another important factor to consider is the
geometry of the molecule. Take time to read and analyze the figures below. Refer to
your periodic table for the electronegativities (X) of the elements.
Figure 7. Comic representation of the
carbon dioxide (CO2) molecule
Figure 8. Comic representation of the
water (H2O) molecule
The bonds between C (2.5) and O (3.5) in Figure 7 are polar each with an
electronegativity difference of (/2.5 – 3.5/ =) 1.0.
However, the linear geometry of the molecule aligning the C atom between the
two O atoms balances the polarity in the bonds with both ends of the molecule
becoming negatively charged. This makes the overall molecule nonpolar (figure 7).
The water (H2O) molecule is another example of how the geometry of the
molecule affects its polarity. While the bonds between H and O atoms are polar, its
bent shape points the two positively charged H atoms away from the negatively
charged O atom, thereby making it a polar molecule (figure 8).
Valence Shell Electron Pair Repulsion (VSEPR) theory
The Lewis electron dot diagram and the concept of chemical bonding
introduced in your junior high school science are useful in determining the geometry
or overall shape of a given molecule together with the valence shell electron pair
repulsion (VSEPR) theory. The VSEPR theory is a guide for us to predict the
arrangement of atoms in a polyatomic molecule. In determining the geometry of a
molecule, we need to identify the central atom first. Usually, the least numerous
element, the least electronegative element, or the element which can form the most
bonds is the central atom. Hydrogen can never be the central atom (except in H2) as
it can only form one bond.
In the water (H2O) molecule, the central atom is oxygen since it is the least
numerous element and can form more bonds than hydrogen.
1. Create the appropriate Lewis dot structure of the molecule.
Source:
https://commons.wikimedia.org/wiki/
File:H2O_Lewis_Structure_PNG.png
4
2. Using the Lewis structure as a guide,
determine the appropriate VSEPR shape
for the molecule. The number of
electrons that are shared or bonded
including the lone pairs will help
determine the appropriate VSEPR
shape.
Source:
https://commons.wikimedia.org/wiki/File:H2O_Lewis_Structu
re_PNG.png
Based on the Lewis dot structure, the
molecule of water has two (2) bonded
pairs and two (2) lone pairs.
Given the Lewis dot structure of H2O above, we can then use the following
table to determine its molecular geometry.
VSEPR MOLECULAR SHAPES
No. of bonded
pairs
No. of Lone
pairs
Arrangement
of electron
pairs
Molecular
Geometry
Examples
2
0
Linear
CO2
2
1
Bent
SO2
3
0
Trigonal
Planar
BCl3
4
0
Tetrahedral
CH4
3
1
Trigonal
pyramidal
NH3
2
2
Angular / Bent H2O
5
0
Trigonal
bipyramidal
PCL5
6
0
Octahedral
SF6
https://www.lamar.edu/arts-sciences/_files/documents/chemistry-biochemistry/dorris/chapter9.pdf
5
We can now see that the molecular geometry shape of a water molecule is
angular or bent. Moreover, looking at the overall polarity of the water molecule we
can therefore say that water is a polar molecule, since it has polar covalent bonds
between H and O, and it has an asymmetrical molecular geometry shape that is
angular/bent. Remember, when the molecule is symmetrical, it is most often
nonpolar. When the molecule is asymmetrical, it is most often polar.
Polar molecules:
Molecule
Lewis Dot Structure
Molecular Geometry
Polarity
H2 O
Angular
polar
NH3
Trigonal pyramidal
polar
NO
Linear
polar
Source: https://www.masterorganicchemistry.com/2010/08/14/from-gen-chem-to-org-chem-pt-7-lewisstructures/
Nonpolar molecules:
Molecule
CO2
Lewis Dot Structure
Molecular Geometry
Polarity
Linear
nonpolar
CH4
Tetrahedral
nonpolar
CCl4
Tetrahedral
nonpolar
Source: https://www.masterorganicchemistry.com/2010/08/14/from-gen-chem-to-org-chem-pt-7-lewisstructures/
6
Let Us Practice
Activity 1: Determining Bond Polarity
Silicones are polymeric compounds containing, among others, the
following covalent bonds:
Si–O, Si–C, C–H, and C–C.
1. Copy and fill-out the table below.
2. Compute for the electronegativity difference between the bonds given
the electronegativity values (X) of the following elements:
Si = 1.8
O = 3.5
C = 2.5
H = 2.1
3. Determine whether the type of bond formed between the atoms is ionic,
polar covalent, or nonpolar covalent bonds using the table of
electronegativity and bond type on page 3.
Atoms Involved
Electronegativity Difference
Type of Bond
Si and O
Si and C
C and H
C and C
Guide Questions:
1. Which atoms shared nonpolar covalent bonds?
2. Which atoms shared polar covalent bonds?
3. Are there atoms that share ionic bonds? Why or why not?
Let Us Practice More
Activity 2: Determining Polarity of Molecules
After learning how to determine whether a bond is polar or nonpolar by
computing for its electronegativity, let us now determine the polarity of the
molecule. Ready? Let’s do it!
Determine if the given molecule is polar or nonpolar by filling-out the
needed information. Answer in a separate sheet. The first one has been done
for you.
7
Molecule
Electronegativity
(Atoms
Involved)
Electronegativity
Difference
(absolute
value)
Bond
Polarity
(between
atoms)
Water
(H2O)
H = 2.1
O = 3.5
1.4
Polar
covalent
1. Oxygen
gas (O2)
O = 3.5
O = 3.5
2.
Formaldehyde
(CH2O)
3.
Carbon
tetrafluoride
(CH4)
Lewis Dot
Structure
Molecular
Geometry
Molecular
Polarity
bent
polar
C = 2.5
H = 2.1
C = 2.5
O = 3.5
C = 2.5
H = 2.1
4.
Hydrogen
cyanide
(HCN)
5.
Ammonia
(NH3)
C = 2.5
H = 2.1
C = 2.5
N = 3.0
N = 3.0
H = 2.1
Let Us Remember
Through this module, you have learned the following important concepts about
polar and nonpolar.
•
•
•
•
The polarity of a molecule is determined by the type of covalent bond
present in the molecule and its molecular geometry.
Electrons in a polar molecule are not evenly distributed resulting to a
partial positive and partial negative side while electrons in a nonpolar
molecule are evenly distributed and are usually symmetrical in shape.
Electronegativity difference between atoms determine the type of bond
they share. The higher the difference the more polar is the bond.
VSEPR theory is a useful tool to predict the probable shape of molecules.
8
•
•
•
Basic shapes in molecular geometry include linear, bent, trigonal
planar, tetrahedral, trigonal bipyramidal and octahedral.
A molecule with polar bonds is not necessarily a polar molecule. A
molecule is polar when it contains at least one polar bond and has an
asymmetric structure.
As a general rule “like dissolves like” so polar substances mix well with
other polar substances, but not with nonpolar substances. Like in our
earlier experiment, oil and water never mix because their molecules
have different polarities.
Let Us Assess
Read the questions carefully. Choose the best answer and write it on a
separate sheet of paper.
1.
Which statement below best describes the structure of a polar molecule?
A. The molecule is symmetrical.
B. Both ends are positively charged.
C. Both ends are slightly negatively charged.
D. One end is positively charged and the other is negatively charged.
2.
Which of the following molecules is polar?
A. Cl3
C.
B. CS2
D.
3.
Which among the following factors does not contribute to the overall polarity
of the molecule?
A. Type of bond formed between atoms
B. Symmetry of the molecular structure
C. Electronegativity differences between bonding atoms
D. Difference in atomic masses of each element in the molecule
4.
Which among the substances below represents a polar molecule?
A. F2
C. CH4
B. NH3
D. CO2
5.
What is the molecular geometry shape, and overall polarity of an SO3
molecule?
A. Trigonal Planar, Polar
C. Trigonal Pyramidal, Polar
B. Trigonal Planar, Nonpolar
D. Trigonal Pyramidal, Nonpolar
6.
Which statement best explains why carbon tetrachloride (CCl 4) is a nonpolar
molecule?
A. The carbon tetrachloride molecule is symmetrical.
B. Carbon tetrachloride is an organic compound.
C. Carbon and chlorine are both nonmetals.
D. Each carbon-chloride bond is polar.
9
PF4
CCl4
7.
Which of the following reasons BEST explains why a water molecule is
polar?
A. It has polar covalent bonds.
B. The electronegativity difference is high.
C. It has a bent molecular geometry shape.
D. The overall molecular shape is symmetrical
8.
Which of the following pairs has both nonpolar molecules?
A. CO and CH4
C. CO2 and CH4
B. H2O and CO
D. CO and CO2
9.
What is the reason why polar molecules have partial charges towards the
opposite ends of the molecule?
A. complete loss of electrons
B. uneven electron distribution
C. average distribution of electrons
D. uneven number of electron pairs
10. Which of the following molecular geometry shapes is most likely to be a
polar molecule?
A. Bent
C. Tetrahedral
B. Linear
D. all of the above
11. Based on their molecular geometry shape, which of the following is a
nonpolar molecule?
A. H2O - bent
C. CClH3 - tetrahedral
B. CO2 - linear
D. NH3 - trigonal pyramidal
12. Based on the structure of carbon tetrachloride, which of the following
statements is TRUE?
Carbon Tetrachloride (CCl4)
A.
B.
C.
D.
It is polar because it is a tetrahedral molecule.
It is nonpolar because of its symmetrical structure.
It is polar due to the high electronegativity difference of C & Cl atoms.
It is nonpolar because the bonds between C & Cl atoms are nonpolar.
13. Which of the following statements is TRUE about nonpolar molecules?
A. They contain only nonpolar covalent bonds.
B. Some nonpolar molecules have polar bonds.
C. Nonpolar molecules have lone pairs of electrons
D. Nonpolar molecules are structurally asymmetrical.
14. Why is NH3 classified as a polar molecule?
A. It is a gas.
B. N-H bonds are nonpolar.
C. Nitrogen and hydrogen are both nonmetals.
D. NH3 molecules have asymmetrical charge distributions
10
15. Which of the following molecular structures represent a nonpolar molecule?
A.
C.
B.
D.
Let Us Enhance
Activity 3: Epic Comic Strip
After learning the lesson of this module, it is time to apply what you
have learned. This will be done for you to find the connection and meaning of
the lesson to your personal life. Please read and appreciate the article pinned
on the next page.
After reading the news article, make sense of your realizations by
making a comic strip that features a conversation on proper handwashing,
and the application of the concepts of polar and nonpolar molecules to the
prevention of the spread of infectious diseases.
Your comic should include the basic elements like title, author, and at
least 6 panels/frames, it should also include at least 2 interacting characters.
Use drawings to portray what has happened in the story. Also, use dialogue
bubbles to express what the characters are saying or feeling. Use the rubric
on the succeeding page as your guide in making an Epic comic strip!
11
HERE’S WHY WASHING YOUR HANDS WITH SOAP FOR 20 SECONDS PROTECTS
YOU FROM COVID-19
by Roberto Molar Candanosa
From News@Northeastern, March 20, 2020
https://news.northeastern.edu/2020/03/20/heres-why-washing-your-handswith-soap-for-20-seconds-protects-you-from-covid-19/
Scientists say that even with the best and most expensive research available, a
vaccine against SARS-CoV-2, the virus that causes COVID-19, is at least a year away.
Scientists also say that the worst enemy of the virus is that cheap soap by your sink.
That’s because of simple chemistry. In soap lather, a combination of molecules
assembles into bubble-like structures called micelles that trap viral matter and other
biomaterials—grease, oil, dirt—and rinse them down the drain.
The soaps we use contain a class of compounds called surfactants, which can
neutralize germs in our skin such as SARS-CoV-2 and other coronaviruses,
pathogens with a crown-like structure and an outer membrane made of lipid
molecules and proteins. So, how does soap clean the dirt, grease, and oils off of your
hands?
You’ve heard the saying – oil and water do not mix. On a chemical level, that’s
because the fatty molecules that make up oil, grease, and dirt are all non-polar
molecules that don’t have a charge, while water molecules are polar. That’s why you
get separate layers when you mix cooking oil with water or vinegar. This is important
to understand for handwashing, because when disease-causing germs in fecal matter
or dirt get on your hands after using the toilet or touching a contaminated surface,
they mix with the natural oils on your skin and stay there. When you rinse your
hands with water only, it’s ineffective against the germy oils that have lodged onto
your skin. The water slips right off without mixing, just like it does with cooking oil.
That’s where soap comes in. Because soap is salt derived from an oil or fat, it has a
unique chemical structure that looks like a balloon. The balloon head is the salt—a
charged, polar molecule—and it’s connected to a string or tail of non-polar fatty
acids. The soap molecule can therefore act like a double-agent: the salty end is
attracted to water, while the fatty tail is attracted to the dirt or oil. When you mix
soap with dirt and water, the soap molecules break up the dirt and the bacteria it
contains by forming circles around individual droplets—the fatty chains go in the
middle facing the dirt, while the salt balloon tops form the outside of the circle facing
the surrounding water.
12
RUBRIC FOR COMIC STRIP MAKING:
Criteria
Basic
Elements
4
The comic
strip has all
the basic
elements
completed
Layout
All panels
are well
organized
and present
an excellent
flow of idea
to the comic
strip
All drawings
are
completed,
colored,
organized,
clear, and
have a logical
presentation.
Illustrations
Grammar
and usage
There are no
grammar or
usage errors
3
The comic
strip has one
of the basic
elements not
completed or
missing
2
The comic
strip has two
basic
elements not
completed or
missing
1
The comic
strip has
three or
more basic
elements not
completed or
missing
All panels
Few panels
Most panels
are organized are
are
and present
unorganized unorganized
a flow of idea and the flow and there is
to the comic
of idea in the no flow of
strip
comic strip is idea to the
not clear
comic strip
1-2 drawings
are not
completed,
colored,
organized,
clear, or have
a logical
presentation.
3-4 drawings
are not
completed,
colored,
organized,
clear, or have
a logical
presentation.
There are at
least 2
grammar or
usage errors
There are at
least 5
grammar or
usage errors
5 or more
drawings are
not
completed,
colored,
organized,
clear, or have
a logical
presentation.
There are
more than 5
grammar or
usage errors
Let Us Reflect
Polarity of molecules serve as the basis for many important biological processes to
occur. The cell membranes that are made up of phospholipids rely on polarity. The
mechanism of protein synthesis and folding are also dependent on polarity of
molecules. Learning through this module helps you appreciate not just the concept
of polarity but also its real-life applications in medical, food, and other industries.
13
Let Us Enhance
(answers vary)
14
Let Us Practice More
Activity 2
Let Us Assess
1. D
2. A
3. D
4. B
5. B
6. D
7. C
8. C
9. B
10. A
11. B
12. B
13. B
14. D
15. D
Let Us Practice
Activity 1
Atoms
Electronegativity
Involved
Difference
0
C and C
0.4
C and H
0.7
Si and C
1.7
Si and O
Let Us Try
Type of Bond
Polar covalent
Polar covalent
1.
2.
3.
4.
5.
D
D
D
A
B
Nonpolar covalent
Nonpolar covalent
Guide Questions
1. (answers vary)
2. (answers vary)
3. (answers vary)
Answer Key
References
Candalosa, R. M. (2020). "Here’s why washing your hands with soap for 20 seconds
protects you from covid-19." news.northeastern.edu. 03 20. Accessed 06 5,
2020.
https://news.northeastern.edu/2020/03/20/heres-why-washingyour-hands-with-soap-for-20-seconds-protects-you-from-covid-19/.
n.d. "Chapter 9: Molecular Geometries and Bonding Theories." lamar.edu. Accessed
06
10,
2020.
https://www.lamar.edu/artssciences/_files/documents/chemistry-biochemistry/dorris/chapter9.pdf.
Education, Commission on Higher. 2016. Teaching Guide for Senior High School
Physical
Science.
https://drive.google.com/file/d/0B869YF0KEHr7SHFGVG5mVFFhcXc/view
.
George, Adrian V. n.d. "Shape of Molecules." sydney.edu.au. Accessed 06 05, 2020.
https://www.sydney.edu.au/science/chemistry/~george/1108/ShapesOfMo
lecules.pdf.
Kallen, Laura Edison. 2019. "HOW DOES SOAP ACTUALLY WORK?" defeatdd.org.
August 28. Accessed 06 10, 2020. https://www.defeatdd.org/blog/how-doessoap-actually-work.
n.d.
Lewis Structures, Shapes, and Polarity. Accessed 06 10, 2020.
https://www.everettcc.edu/files/programs/academicresources/transitional-studies/support/tutoring-center/chemistry/w319lewis-structures-shapes-and-polarity.pdf.
Ma. Cristina D. Padolina, PhD. 2004. Conceptual and Functional Chemistry:
Modular Aproach. Metro Manila: Vibal Publishing House.
2020.
Oil
and
Water
Experiment.
Accessed
06
10,
https://www.growingajeweledrose.com/2013/04/science-for-kidsexperiments.html.
2020.
2013. Polar & Non-Polar Molecules: Crash Course Chemistry #23. July 22. Accessed
06 10, 2020. https://www.youtube.com/watch?v=PVL24HAesnc&t=131s.
2015. Polar and NonPolar Molecules: How To Tell If a Molecule is Polar or Nonpolar.
September
28.
Accessed
06
10,
2020.
https://www.youtube.com/watch?v=SiZXRScxbl0.
n.d.
Polar
Molecules.
Accessed
06
10,
2020.
https://courses.lumenlearning.com/cheminter/chapter/polar-molecules/.
Shipman, James T. 2016. An Introduction to Physical Science. 14. Sampaloc, Manila:
Rex Book Store, Inc.
n.d. Valence-Shell Electron-Pair Repulsion Theory (VSEPR). Accessed 06 07, 2020.
https://chemed.chem.purdue.edu/genchem/topicreview/bp/ch8/vsepr.htm
l.
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