POLARITY OF MOLECULES - Part I | ELECTRONEGATIVITY DIFFERENCE | Physical Science
Summary
TLDRIn this physical science lesson, students explore the concept of molecular polarity through an experiment mixing water, dishwashing liquid, and cooking oil. The video explains that polarity arises from the unequal sharing of electrons, exemplified by water's polar nature and oil's nonpolar status. It delves into electronegativity, dipole moments, and how they contribute to a molecule's polarity. The lesson also touches on the electronegativity scale and the impact of molecular geometry, using carbon dioxide as an example of a linear, nonpolar molecule despite polar bonds. The content is designed to help students distinguish between polar and non-polar molecules.
Takeaways
- 🧪 The lesson is about understanding the polarity of molecules and distinguishing between polar and non-polar molecules.
- 🥣 An experiment is conducted to observe the interaction between water, dishwashing liquid, and cooking oil, illustrating the difference in polarity.
- 🌊 Water and oil do not mix because water is a polar molecule and oil is non-polar, demonstrating the concept of polarity through a simple example.
- ⚛️ Polarity arises from the unequal or asymmetrical distribution of electrons in a molecule, leading to a partial charge difference.
- 🔍 The molecular structure of water is highlighted, showing how oxygen and hydrogen atoms share electrons unequally due to differing electronegativities.
- 💪 Electronegativity is the ability of an atom to attract electrons in a bond, with oxygen being more electronegative than hydrogen.
- 📊 The concept of a dipole moment is introduced, where the unequal sharing of electrons creates a positive and negative pole in a molecule.
- 🔗 Nonpolar molecules are formed when there is equal or symmetrical distribution of electrons, as in the case of oxygen gas (O2).
- 📊 The electronegativity difference between atoms in a molecule can be used to determine the type of bond: non-polar covalent, polar covalent, or ionic.
- 📚 The periodic table is used to find the electronegativity values of elements, which helps in understanding the polarity of molecules.
- 🏗️ The shape of a molecule also plays a crucial role in its polarity, as seen in the example of carbon dioxide being a non-polar molecule despite having polar bonds.
Q & A
What is the main topic of the physical science class in the video?
-The main topic of the class is the polarity of molecules, focusing on the difference between polar and non-polar molecules.
What experiment is conducted in the video to demonstrate the concept of polarity?
-The experiment involves mixing water, dishwashing liquid, and cooking oil to observe their behavior, illustrating the difference between polar (water) and non-polar (oil) substances.
Why do water and oil not mix according to the video?
-Water and oil do not mix because water is a polar molecule and oil is a non-polar molecule, which means they have different electron sharing characteristics.
What is the significance of the electronegativity of an atom in the context of polarity?
-Electronegativity is the ability of an atom to attract electrons in a bond, which determines whether the sharing of electrons is equal or unequal, thus affecting the polarity of a molecule.
How is the polarity of a molecule represented in the video?
-Polarity is represented by a dipole moment, which is indicated by an arrow pointing towards the more electronegative atom, showing the direction of the partial negative charge.
What is the octet rule and how does it relate to the formation of water molecules?
-The octet rule states that atoms tend to gain, share, or transfer electrons to achieve a stable electron configuration, often eight electrons in their outermost shell. In water, oxygen shares electrons with hydrogen to fulfill this rule, forming a polar covalent bond.
How can the polarity of a molecule be determined based on electronegativity differences?
-The polarity of a molecule can be determined by the electronegativity difference between the atoms in the molecule. If the difference is 0 to 0.4, it's non-polar covalent; 0.5 to 2.0, it's polar covalent; and above 2.1, it's ionic.
What is the electronegativity difference between hydrogen and oxygen in a water molecule?
-The electronegativity difference between hydrogen (2.1) and oxygen (3.5) is 1.4, which falls within the polar covalent bond range, making water a polar molecule.
Why is oxygen gas (O2) considered a non-polar molecule despite being composed of oxygen atoms?
-Oxygen gas is non-polar because the two oxygen atoms have the same electronegativity and share electrons equally, resulting in no dipole moment and an even distribution of electron density.
Can the shape of a molecule affect its polarity even if the bonds are polar?
-Yes, the shape or molecular geometry can affect the overall polarity of a molecule. For example, carbon dioxide has polar bonds but is non-polar overall due to its linear shape, which distributes the charge evenly.
What will be discussed in the next video according to the script?
-The next video will discuss molecular geometry and the shape of molecules, which is another factor in determining the polarity of a molecule.
Outlines
🔬 Introduction to Molecular Polarity
This paragraph introduces the topic of molecular polarity within a physical science class setting. The instructor explains the concepts of polar and non-polar molecules and sets up an experiment involving water, dishwashing liquid, and cooking oil to illustrate these concepts. The experiment aims to demonstrate the difference in behavior when polar and non-polar substances are mixed. The paragraph concludes with a brief introduction to the concept of polarity arising from the unequal sharing of electrons among atoms in a molecule.
🌟 Understanding Polarity and Non-Polarity in Molecules
The second paragraph delves deeper into the molecular structures that define polarity and non-polarity. It explains that a polar molecule has an unequal or asymmetrical distribution of electrons, using water as an example where the oxygen atom has a higher electronegativity than hydrogen, resulting in a partial negative charge on oxygen and a partial positive charge on hydrogen. This creates a dipole moment. In contrast, non-polar molecules have a symmetrical distribution of electrons, as demonstrated with oxygen gas (O2), where the electron density is evenly spread due to equal electronegativity between the atoms. The paragraph also introduces the concept of electronegativity and how it can be used to determine the type of bond in a molecule, with a focus on the difference in electronegativity values indicating the bond polarity. It concludes with a teaser for the next video, which will discuss molecular geometry's role in determining molecular polarity.
Mindmap
Keywords
💡Polarity
💡Molecules
💡Electronegativity
💡Dipole Moment
💡Nonpolar Molecules
💡Polar Molecules
💡Valence Electrons
💡Octet Rule
💡Electronegativity Difference
💡Molecular Geometry
Highlights
Introduction to the concept of molecular polarity in physical science class.
Experiment involving water, dishwashing liquid, and cooking oil to demonstrate polarity.
Observation of how water and dishwashing liquid do not mix with oil due to polarity differences.
Explanation of electron sharing and the concept of polar and non-polar molecules.
Description of water as a polar molecule due to its molecular structure and electronegativity differences.
Illustration of the octet rule and how atoms share, gain, or transfer electrons to achieve stability.
Introduction of the term 'electronegativity' and its role in determining molecular polarity.
Explanation of how the unequal sharing of electrons creates a dipole moment in polar bonds.
Comparison of polar and non-polar bonds through the tug of war analogy.
Use of oxygen gas (O2) as an example of a non-polar molecule with symmetrical electron distribution.
Introduction of the electronegativity difference scale to determine bond polarity.
Demonstration of how to calculate electronegativity difference using the periodic table.
Clarification that molecular polarity also depends on molecular geometry, not just bond type.
Example of carbon dioxide as a molecule with polar bonds but non-polar overall due to its linear shape.
Teaser for the next video on molecular geometry and its impact on molecular polarity.
Conclusion of the lesson with a summary of the key points on molecular polarity.
Transcripts
hello green 11
welcome to our physical science class
today
you will learn about the polarity of
molecules
we will try to understand the difference
between the two types of molecules
according to polarity the polar
molecules
and the non-polar molecules at the end
of this video
you should be able to determine if a
molecule is polar
or non-polar bored
for today's lesson let's do this simple
experiment first
we will observe how water and
dishwashing liquid
behave when they are mixed with a
cooking oil
to do this we will be needing a water
a cooking oil a dish washing liquid
and a steering rod let's do it
first elegant nutella and too big and
cooking oils hello all numbers too
[Music]
then mix
what do you notice i'm too big at
matica island i hindi magni mix
now let's try the dishwashing liquid and
the cooking oil
let's see
[Music]
video
polarity happens when there is equal or
unequal sharing of
electrons among the atoms of a molecule
in the case of water and oil they will
never mix
because water is a polar molecule while
oil is a nonpolar molecule now let's
take a closer look at how these two
types of molecules differ
a molecule is said to be polar when
there is unequal or asymmetrical
distribution of
electrons what does this mean
water for example is a molecule composed
of two hydrogen atoms
and one oxygen atom if we are going to
draw the molecular structure
of oxygen atom you will notice that it
has only 6 electrons
in its outermost shell we call this the
valence electron
as discussed when you were in grade 9
octet rule
states that atoms tend to gain share
or transfer electrons in order to attain
a complete set of valence electron
configuration
therefore oxygen needs two more
electrons to become
stable hydrogen however is an exemption
to the rule
since it has only one electron in its
shell
to become stable hydrogen needs one more
electron
[Music]
they will share electrons with each
other oxygen will share its electron to
hydrogen
and hydrogen to oxygen forming water
molecule
oxygen now has eight electrons and
hydrogen has
two making each atom stable
now this relative ability of an atom to
draw electrons in a bond toward itself
is called electronegativity of the atom
then with maraming or denser and
electrons than oxygen
compared to hydrogen negatives and
connect
giving it a partial negative charge
on the other side hydrogen has a lower
electronegativity
partial positive charge this unequal
sharing of electrons between
atoms creates a dipole moment or two
poles
the positive and the negative we will
represent this with a with an
arrow pointing towards oxygen since
oxygen
is more electronegative than hydrogen
the sharing of electrons by two atoms
may be likened to a tug of war between
two men
the stronger man drags the other across
a central line between atoms the shared
electron
pair is attracted more strongly toward
the negative atom making them
unequal or asymmetrical creating a polar
bond
nonpolar molecules however are formed
when there is equal or symmetrical
distribution of
electrons this happens when the bonding
atoms have approximately equal ability
to attract electrons on each side
let's have oxygen gas o2 as an example
as we have discussed earlier oxygen has
six valence electrons so
when two oxygen atoms with the same
electronegativity
combined that will happen as you can see
the electron density is spread evenly
between the two atoms
in the band since a pair of electrons is
shared
equally between atoms there is no
partial
charge created hence no dipole moment
therefore oxygen gas is a non-polar
molecule
we can also determine the polarity of
molecules based on the electronegativity
difference between the atoms present in
a molecule to get the electronegativity
value of each element we will use a
periodic table
there you can see the electronegativity
value of
each element electronegativity value
increases from left to right which means
that non-metals
are more electronegative than metals
in the table you can see that oxygen and
fluorine have the highest
electronegativity volume
so we have to remember this bond range
if the electronegativity difference
range from 0 to 0.4
the type of bond is non-polar covalent
0.5 to 2.0 it is a polar covalent bond
and when the value is 2.1 above
the molecule is in an ionic bond now
let's use again water as an example
the electronegativity value of hydrogen
is 2.1
and oxygen is 3.5
to get the electronegativity difference
we simply subtract 2.1 from
3.5 this becomes 1.4
so since the value is 1.4 and is within
the 0.5 to 2.01 range
water is polar the greater the
difference between the electronegativity
of the atoms involved in the bond
the greater is the polarity of the
molecule
for the oxygen gas o2 the
electronegativity
value of oxygen is 3.5 therefore
3.5 minus 3.5 is
0. so this is within the bond range of 0
to 0.4 which means that oxygen
is a non-polar covalent that's simple
however the polarity of molecules do not
depend
solely on the type of bond present but
also on the shape
of the molecules this means that there
are molecules who are polar
in bonding but is actually a nonpolar
molecule
based on the shape of the molecules
maybe you're now wondering how it
happened
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let's use carbon dioxide as an example
carbon has four electrons and oxygen has
six
so carbon needs four and oxygen needs
two to become stable
therefore the two oxygen atom will share
its electrons to carbon making them
stable since oxygen is denser it gains
a partial negative charge and carbon a
partial positive charge
making it a polar molecule
in terms of the electronegativity the
electronegativity value of oxygen is 3.5
and carbon is 2.5 giving them
an electronegativity difference of 1.0
making the molecule a polar bond however
based on the molecular geometry or the
shape of the molecules
carbon dioxide is a linear molecule
making it
a non-polar molecule we will discuss
this topic about molecular geometry or
the shape
of the molecules in our next video
and that ends our lesson i hope you
learned something today
thank you for watching
[Music]
you
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