POLARITY OF MOLECULES - Part I | ELECTRONEGATIVITY DIFFERENCE | Physical Science

Summary

In 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

00:00

🔬 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.

05:01

🌟 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.

Keywords

💡Polarity

Polarity refers to the condition where there is an unequal distribution of electric charge across a molecule, resulting in two poles, one positive and one negative. In the video, polarity is central to understanding why water and oil do not mix, as water is a polar molecule and oil is nonpolar. The concept is illustrated through the experiment with water, dishwashing liquid, and cooking oil, showing that the polar water molecule forms a dipole moment due to the difference in electronegativity between hydrogen and oxygen atoms.

💡Molecules

Molecules are the smallest particle in a chemical element or compound that has the chemical properties of that element or compound. The video discusses two types of molecules based on polarity: polar and non-polar. The script uses water and oxygen gas as examples to explain the difference between polar and non-polar molecules, with water being polar due to its asymmetrical charge distribution and oxygen gas being nonpolar due to its symmetrical electron sharing.

💡Electronegativity

Electronegativity is a measure of the tendency of an atom to attract a shared pair of electrons, with the scale ranging from 0 to 4. In the video, electronegativity is key to determining the polarity of a molecule. For instance, oxygen is more electronegative than hydrogen, which results in an unequal sharing of electrons and a partial negative charge on the oxygen atom in a water molecule, contributing to its polarity.

💡Dipole Moment

A dipole moment is a measure of the separation of positive and negative electrical charges in a molecule, which results in a molecule having two poles. The video explains that the water molecule has a dipole moment because the oxygen atom attracts the shared electrons more strongly than the hydrogen atoms, creating a partial negative charge on oxygen and a partial positive charge on hydrogen.

💡Nonpolar Molecules

Nonpolar molecules are those in which the electrons are shared equally between atoms, resulting in no separation of charge and no dipole moment. The video uses the example of oxygen gas (O2) to illustrate nonpolar molecules, where the electronegativity of the two oxygen atoms is the same, leading to an even distribution of electron density and no partial charges.

💡Polar Molecules

Polar molecules are those with an unequal distribution of electron density, leading to a separation of charge and the formation of a dipole moment. The video script explains that water is a polar molecule because of the difference in electronegativity between hydrogen and oxygen, which causes an asymmetrical distribution of electrons and a partial charge separation.

💡Valence Electrons

Valence electrons are the electrons located in the outermost shell of an atom and play a key role in chemical bonding. The video mentions valence electrons in the context of the octet rule, stating that atoms tend to gain, share, or transfer electrons to achieve a stable configuration, often eight electrons in the outer shell. For example, oxygen needs two more electrons to complete its valence shell, while hydrogen needs one.

💡Octet Rule

The octet rule is a chemical rule of thumb that states atoms tend to form bonds in ways that result in each atom having eight electrons in its valence shell, giving it the same electronic configuration as the nearest noble gas. The video uses the octet rule to explain how oxygen and hydrogen form a stable water molecule by sharing electrons to complete their valence shells.

💡Electronegativity Difference

Electronegativity difference is the numerical difference in electronegativity values between the atoms in a covalent bond. The video explains that if the electronegativity difference is between 0 to 0.4, the bond is non-polar covalent, and if it's between 0.5 to 2.0, it is a polar covalent bond. For water, the electronegativity difference between hydrogen (2.1) and oxygen (3.5) is 1.4, indicating a polar covalent bond.

💡Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. The video script mentions that the polarity of a molecule can also be influenced by its shape, not just by the type of bond or electronegativity difference. For example, carbon dioxide, despite having polar bonds due to the electronegativity difference between carbon and oxygen, is a nonpolar molecule because of its linear molecular geometry, which distributes the charge evenly.

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