2.3 Structures and Properties of Material

Summary

In this chemistry lesson, the instructor explores the particulate nature of matter, focusing on the differences between elements, compounds, and mixtures. They explain that elements consist of a single type of atom and cannot be broken down, while compounds are made of two or more different elements chemically bonded together. Mixtures, on the other hand, are physical combinations of different elements that can be separated without chemical processes. The instructor also delves into the structures and properties of simple molecular substances, giant covalent substances, and provides detailed comparisons between diamond and graphite, including their bonding, physical properties, and uses. The lesson concludes with practice examples to reinforce the concepts discussed.

Takeaways

• 🔬 Elements are pure substances consisting of only one kind of atom and cannot be broken down into simpler substances by chemical means.
• 🧪 Compounds are made up of two or more different elements chemically bonded together and can be separated by chemical means but not by physical means.
• 🌐 Mixtures consist of two or more different elements combined physically and can be separated by physical means without any chemical intervention.
• 📚 Metallic elements are represented by atomic symbols and are found on the left-hand side of the periodic table, while non-metals are on the right.
• 💧 Non-metallic elements often exist as molecules, which are made up of two or more atoms of the same element chemically bonded together.
• 🌀 Noble gases, found on the right side of the periodic table, exist as separate atoms and are represented by their own symbols.
• 🔑 Compounds have fixed proportions of their component elements and different properties from their constituent elements, whereas mixtures have variable ratios and retain the properties of their components.
• 🌡 Simple molecular substances have weak intermolecular forces, leading to low melting and boiling points, while giant covalent substances have strong covalent bonds resulting in high melting and boiling points.
• 🔥 When burned, both graphite and diamond, being forms of carbon, produce carbon dioxide, indicating they are composed of the same element but in different structural forms.
• ⚙️ Graphite has a layered hexagonal structure with weak forces between layers, making it soft and a good conductor of electricity, while diamond has a tetrahedral structure with strong covalent bonds, making it hard and an electrical insulator.

Q & A

What are the three main categories of substances discussed in the script?

The three main categories of substances discussed are elements, compounds, and mixtures.

What is the defining characteristic of an element?

An element is a substance that cannot be broken down into simpler substances and consists of only one kind of atom.

How do compounds differ from mixtures in terms of their composition?

Compounds are made up of atoms of two or more different elements bonded together by chemical bonds, while mixtures consist of two or more different elements combined physically without chemical bonding.

What is the difference between metallic and non-metallic elements in the periodic table?

Metallic elements are represented by atomic symbols and are found on the left-hand side of the periodic table, while non-metallic elements exist as molecules or separate atoms, particularly the noble gases, and are found on the right-hand side.

Why do simple molecular substances have low melting and boiling points?

Simple molecular substances have low melting and boiling points because they have weak intermolecular forces that require only a small amount of energy to break.

What is the key difference between the structures of graphite and diamond?

Graphite has a layered hexagonal structure with carbon atoms directly attached to three other carbon atoms, while diamond has a tetrahedral structure with each carbon atom bonded to four other carbon atoms.

Why does graphite conduct electricity while diamond does not?

Graphite conducts electricity because it has free-moving electrons that are not involved in covalent bonding between the carbon atoms, whereas in diamond, all electrons are involved in strong covalent bonds, leaving no free electrons to conduct electricity.

What are the physical properties of simple molecular substances at room temperature and pressure?

Simple molecular substances can be solids, liquids, or gases at room temperature and pressure, and they are highly volatile, easily evaporating due to their weak intermolecular forces.

How do the properties of compounds differ from those of their constituent elements?

Compounds have different properties from their constituent elements because the chemical bonding in compounds results in new properties that are distinct from those of the individual elements.

What is an allotrope and how does it relate to the discussion on graphite and diamond?

An allotrope is a different form of the same element with a different structure. Graphite and diamond are allotropes of carbon because they are both made of carbon but have different structural forms.

Outlines

00:00

🔬 Introduction to Chemistry 5070: Particulate Nature of Matter

The speaker begins by introducing the topic of the day, which is the particulate nature of matter, specifically focusing on the structure and properties of materials. The lecture aims to differentiate between elements, compounds, and mixtures. Elements are pure substances consisting of a single type of atom and cannot be broken down further. Compounds are made up of two or more different elements chemically bonded together, and mixtures consist of two or more different elements combined physically. The speaker also discusses the representation of metallic and non-metallic elements on the periodic table, with metals typically found on the left and non-metals on the right. Non-metals often exist as molecules, which are groups of two or more atoms of the same element chemically bonded together. The lecture also touches on noble gases, which are non-metals existing as separate atoms.

05:01

🧪 Properties and Structures of Compounds and Mixtures

This section delves into the properties of compounds and mixtures. Compounds, which are combinations of two or more different elements in fixed proportions, exhibit different properties from their constituent elements. Mixtures, on the other hand, retain the properties of their individual components and can have varying ratios of elements. The speaker uses carbon dioxide as an example to illustrate how compounds form with distinct properties compared to their elements. The lecture also includes a visual diagram to differentiate between atoms, molecules, and compounds within mixtures. The physical properties of simple molecular substances are discussed, highlighting their volatility and low melting and boiling points due to weak intermolecular forces. In contrast, giant covalent substances like diamond and graphite have high melting points due to strong covalent bonds.

10:03

📚 Physical Properties of Simple and Giant Molecular Substances

The speaker continues by discussing the physical properties of simple molecular substances, which can be found in solid, liquid, or gaseous states at room temperature and pressure. These substances are characterized by their volatility and low melting and boiling points due to the ease with which their weak intermolecular forces can be overcome. In contrast, giant molecular substances like silicon dioxide and graphite have higher melting and boiling points. The speaker also notes that while most giant molecular substances do not conduct energy, there are exceptions, such as when acids are dissolved in water, forming ionic bonds that allow for the conduction of electricity. The lecture then transitions into a comparison of the structures of graphite and diamond, both of which are allotropes of carbon but with different physical properties and structures.

15:04

💎 Comparative Study of Graphite and Diamond

This part of the lecture focuses on the structural differences between graphite and diamond, both carbon allotropes. Graphite has a layered hexagonal structure with weak forces between layers, allowing it to conduct electricity and be used as a lubricant due to its softness. Diamond, with a tetrahedral structure, is a 3D network where each carbon atom is bonded to four others, making it extremely hard and an electrical insulator. The speaker highlights the different physical properties of graphite and diamond, such as melting points and electrical conductivity, and discusses their various applications, like graphite in pencil leads and diamond in jewelry and industrial cutting tools.

20:08

⚗️ Chemical Bonding and Melting Points in Substances

The final paragraph addresses the concept of chemical bonding and its impact on the melting points of substances. The speaker explains that substances with ionic bonds, like sodium chloride, have high melting points due to the strength of these bonds. The lecture also covers the identification of different types of substances, such as elements, molecules, and compounds, and their respective structures. The speaker concludes by encouraging questions and further discussion, indicating that more on ionic and covalent bonding will be covered in upcoming lectures.

Keywords

💡Element

An element is a pure substance that consists of only one type of atom and cannot be broken down into simpler substances by chemical means. In the context of the video, the instructor explains that elements are either metallic or non-metallic, with metallic elements located on the left side of the periodic table and non-metallic elements on the right. Examples given include iron (Fe), sodium (Na), and calcium (Ca) for metallic elements, and nitrogen (N2), oxygen (O2), and chlorine (Cl2) for non-metallic molecules.

💡Compound

A compound is a substance formed when two or more different elements are chemically bonded together in fixed proportions. The video emphasizes that compounds have distinct properties from their constituent elements. For instance, carbon dioxide is a compound made of carbon and oxygen, and it exhibits different chemical and physical properties compared to its elemental components.

💡Mixture

A mixture is a combination of two or more different substances where each substance retains its own chemical identity. Unlike compounds, mixtures can be separated by physical means. The script mentions that mixtures can consist of different elements combined physically and can be separated without chemical processes.

💡Metallic Elements

Metallic elements are a category of elements characterized by their tendency to lose electrons and form positive ions. They are typically found on the left side of the periodic table and are represented by their atomic symbols. The video script uses iron (Fe), sodium (Na), and calcium (Ca) as examples of metallic elements.

💡Non-metallic Elements

Non-metallic elements are found on the right side of the periodic table and often exist as molecules made up of two or more atoms of the same element. These elements do not tend to lose electrons as readily as metals. The script discusses how non-metallic elements like nitrogen, oxygen, and chlorine form molecules (N2, O2, Cl2) and how noble gases exist as separate atoms.

💡Molecules

Molecules are groups of two or more atoms bonded together, consisting of the same element, and held together by chemical bonds. The video explains that non-metallic elements form molecules, which are chemically bonded and can be volatile due to weak intermolecular forces. Examples from the script include nitrogen (N2), oxygen (O2), and chlorine (Cl2) molecules.

💡Intramolecular and Intermolecular Forces

Intramolecular forces are the chemical bonds within a molecule, while intermolecular forces act between molecules. The video script explains that intramolecular forces are stronger than intermolecular forces, which are weak and can be easily broken, contributing to the volatility and low melting and boiling points of simple molecular substances.

💡Giant Covalent Substances

Giant covalent substances are a type of chemical structure where atoms are bonded together in a vast network by covalent bonds. Examples given in the video include diamond and graphite, which are both made entirely of carbon atoms but have different structures and properties. These substances have high melting points due to the strength of their covalent bonds.

💡Allotropes

Allotropes are different structural forms of the same element in the same physical state. The video script uses graphite and diamond as examples of allotropes of carbon. Both are made of carbon but have different structures—graphite has a layered hexagonal structure, while diamond has a tetrahedral structure.

💡Physical Properties

Physical properties are characteristics that can be observed or measured without changing the substance's chemical identity. The video discusses how the physical properties of compounds and mixtures differ from their constituent elements. For example, graphite is soft and a good conductor of electricity due to its structure, while diamond is hard and an electrical insulator.

Highlights

Introduction to the particulate nature of matter and the structure and properties of materials.

Differences between elements, compounds, and mixtures explained.

Elements are substances that cannot be broken down into simpler substances and consist of only one kind of atom.

Compounds and mixtures are made up of atoms of two or more different elements bonded together chemically or physically.

Metallic and non-metallic elements are represented differently on the periodic table.

Non-metallic elements exist as molecules or separate atoms, such as noble gases.

Compounds have fixed proportions of elements and different properties from their components.

Mixtures have variable ratios of components and retain the properties of their individual elements.

Simple molecular substances have weak intermolecular forces and are highly volatile.

Giant covalent substances have high melting points due to strong covalent bonds.

Physical properties of simple molecular substances include being solids, liquids, or gases at room temperature.

Giant molecular substances like silicon dioxide have higher melting and boiling points.

Exception in conductivity for covalent substances when dissolved in water, forming ionic solutions.

Comparison of graphite and diamond structures, highlighting their different physical properties.

Graphite's hexagonal layered structure allows it to conduct electricity and act as a lubricant.

Diamond's tetrahedral structure results in a hard material that does not conduct electricity.

Uses of graphite and diamond based on their physical properties, such as lubrication and jewelry.

Practice examples to understand the concepts of elements, compounds, and mixtures.

Discussion on the melting point of magnesium oxide and its strong ionic bonding.

Identification of substances with giant molecular structures and their properties.

Comparison of melting points related to the type of bonding in substances.

Introduction to the concepts of ionic and covalent bonding and their impact on substance properties.

Transcripts

hello my name is teach you guys

chemistry 5070

let's start with today's topic the

particulate nature of matter 2.3

we're going to start with structure and

properties of the materials

i'm going to discuss the differences

between elements compounds and mixtures

and then i'm going to share some simple

molecular substances

they're structures with giant covalent

substances

how do they both uh compare and

i'm going to also share the bonding and

structures of diamond

and graphite so let's begin first i'm

going to

tell you what is the basically an

element compound in mixture

so we all need to know about certain uh

differences between all the three of

them

so elements they are um substances which

they cannot be broken down into simpler

substances

and they consist of only one kind of

atom

so you can see that elements they have

only one kind of atom

and they will not be broken down into

more simpler substances by any kind of

means by physical or chemical means

whereas if i talk about compounds and

mixtures compounds and mixtures they

are made up of atoms of two or more

different kind of elements

they are bounded together by the

chemical bonding

and if you want to separate the

components of a compound

you can separate them by any chemical

means you can separate the elements by

any chemical means but they will not be

separated by physicality

whereas if i talk about mixtures

mixtures they consist

of two or more different elements

and they are combined together

physically

if you want to separate them you can

separate the components by physical

means

and you will not need any chemical means

to separate them

coming to uh these elements elements

they

are substances as i told you that they

cannot be broken down into simpler

substances

by the chemical reactions and elements

can be of two types metallic and

non-metallic

if i talk about metallic elements

metallic elements they

are represented by atomic symbols for

example

the metals they are present on the left

hand side of the periodic table

whereas this is a representation of a

periodic table

so this side is the left hand side which

is made up of metals

whereas the non-metals are present on

the right hand side of the periodic

table

non-metals

right so metals on the left on the left

hand side of the periodic table they are

represented by

the atomic symbols for example iron

sodium calcium they are all represented

by their raman samples

f e iron sodium n a

and calcium c ca

mg for magnesium

right but if i talk about the non-metals

non-metals they exist as molecules

and this is what molecules is all about

molecules they

are made up of two or more

atoms but they are of the same element

for example if i'm talking about the

atoms they are going to be separate

if i'm talking about the molecules they

are going to be

two or more atoms but but they will be

combined together

and they will be of their same element

and they are chemically bounded together

so these are molecules

this image is of a molecule for example

it can be nitrogen

it can be oxygen it can be chlorine n2

o2

cl2 and molecules uh as i told before

that uh the non-metallic elements are on

the

left hand side but if i talk about the

group 8 elements group 8 elements they

consist

of the noble gases and they exist as

separate atoms

so the they will exist at these separate

atoms okay

for example helium argon neon

they will all exist as separate atoms

and e neon helium h e

they are also on the left hand side but

they will exist as separate atoms and

they are represented by their own

symbols

now the compounds they are chemically

combined together and they have two or

more elements

and they are combined in fixed

proportions

so they are they

always contain the same ratio of its

component elements

whereas that mixtures they have

different ratios of their component

elements

if i talk about the properties of the

compounds in the mixtures

the compounds they have different

properties from their component elements

for example carbon dioxide

carbon and oxygen both have different

chemical and physical properties

but when they both are combined together

and they form a carbon dioxide gas they

are going to

have different properties and carbon

dioxide gas will have different

properties

which for example if i talk about

mixtures mixtures they retain their

properties of their own component

elements

so this is the difference between all

three of them

one more thing over here in the diagram

i wanted to show

as you can see these are the atoms these

are the molecules

they are of the same element compound

has

two or more different atoms which are

chemically combined together

as you can see over here in the image in

mixtures you can see we have molecules

as well we have atoms as well and we

have compounds as well

so this is a mixture because it has

different

different components and they are

physically combined together if you want

to separate them they will be physically

separated

coming on to the next slide now

so now i'm going to discuss with you

some simple and

giant molecular substances

now simple molecular substances they can

be

hydrogen oxygen

they all iodine methane carbon dioxide

now they all have

weak intermolecular forces first of all

in a molecule

within a molecule

they have intramolecular forces within a

molecule

and in between the molecules there are

intermolecular forces

so these are intermolecular forces

and within a molecule is the intra

molecule

so intramolecular forces are more

stronger as compared to the

intermolecular forces which are weak

and they are also known as bond evolved

forces if i talk about iodine

it's supposedly this is irene this is i2

so i2 molecules they are going to have

weak intermolecular forces between them

and if you want to break them

they will be easily broken down and

only small amount of energy will be

required to break them down

so they will be highly volatile

and they will have low melting and low

boiling points

this is the reason if someone asks you

why do they have low melting in boiling

points the reason is

that they have lower melting and boiling

points because

only small amount of energy is required

to break the intermolecular forces

because they are weak

whereas if i talk about um giant problem

substances

and covalent substances they have high

melting points

because lots and lots of energy is

required to break

their strong covalent bonds so they have

strong covalent bonds in between for

example

diamond graphite silicon dioxide right

let's come to the next slide now

i'm going to discuss some physical

properties of um

these compounds now simple molecular

substances they are solids liquids and

gases at

vibration and pressure the liquids and

gases at room temperature and pressure

and they have high

they are highly volatile they are going

to um

evaporate very easily because they are

their weak intermolecular forces they

are broken down easily

at room temperature and pressure this is

why they are solid liquids and gases and

room temperature they are solids at room

temperature because

if they are high if they are large

molecules they are going to be

solids if they are smaller molecules

they are going to liquids or gases

for example water and carbon dioxide

simple molecular substances they also

have low melting and boiling points

because

they had they only need small amount of

energy to break their

weak intermolecular forces if i talk

about giant molecule substances for

example silicon dioxide

and graphite environment they have

higher welting and boiling points

problem sometimes they do not at all

conduct energy they will never ever

conduct energy

because they do not have any free moving

electrons to conduct energy

all of their electrons are uh used

up to be shared between the

atoms so except liquefied

and there is another exception for the

covalent substances

if there is an acid and acid is

dissolved in water

what is going to happen it is going to

form um

an accurate solution of acid the acids

they are added into water

they will form an active solution of

the acid and they will the bonding will

convert

into an ionic bonding why because

the ions are going to dissociate and

when the ions are there the

electrons they can carry charges

free moving electrons can carry charges

and that is why they will be able to

conduct electricity so this is an

exception over here

coming to the next slide now

now i am going to compare the structures

of graphite and diamond

before this i am going to tell you one

more thing about

allotropes now allotropes are

let me share it here

allot troops they are of the same

element but they have different

structures

so if the element is the same and they

have different structures

in the same physical state they it will

be known as an electrode

so they have the same element

but they have different structures

for example oxygen o2 and o3

ozone so they both have the same element

but they have

different structure

so they are both known as allots

if i talk about graphite and diamond

they are also

allots because they have the same

element that is carbon

and they are in different structural

forms that is why

they are known as aloe groups now coming

to the

um

differences between the graphite and

diamond and then i will share with you

the physical properties

graphite is has carbon which is directly

attached to

three or more uh carbon atoms

so if you see over here it has one

carbon atom

which is joined to three more carbon

atoms

and it is forming a hexadon hexagon is 6

so it is forming hexagonal structure

which is layered

and whereas if i talk about diamond

diamond has

one carbon atom which is joined to four

more carbon atoms

so it has a tetrahedral structure

so this one is a 3d structure whereas

this one

is a graphite has a 2d structure

so diamonds do not conduct electricity

because all of the

all of the electrons they are used to

share between the different atoms

whereas in graphite

it has one and each carbon has one

electron which is not shared so when one

electron is not

shared so that means they have free

moving electrons so they can conduct

electricity

so graphites can conduct electricity

whereas diamonds they cannot convert

as i shared that graphites they have

layers as well

so as you can see that the layers of

hexagonal layers are formed

in these um in the structure of the

graphite and

in between the carbon atoms we have

coconut bonding whereas between the

molecules we have

weaker binding uh forces or weak

molecular forces which are known as also

wonder walls forces

so these um these

these layers they are they can slide

over each other

which is why they

are the graphite is very soft and they

can be used in

as a lubricant

they have the same formula carbon

c

now coming back to my last slide

so i will share with you the physical

properties

here as i shared

graphite has a lower melting point

whereas diamond has

a higher melting point because it is

hard and it has a stronger covalent

bonding as compared to purifying

equified has some water balls versus

obvious

which is why it has a slightly lower

melting point as compared to that

graphite can conduct electricity whereas

the diamond cannot conduct electricity

because there is no free moving electron

if both are burnt they both are going to

produce carbon dioxide

when both are born they are going both

are going to produce carbon dioxide

as both are made up of carbon and then

they are going to be combusted

and they

so

one more thing now the uses of grapevine

graphite can be used as

a lubricant because it has sliding

layers it is soft and it is very smooth

when it is baked along with clay it will

form

pencilling so if you have more gravity

in pencil lead the layer pencil light is

going to be more softer

why because it has a properties graphite

has a property of being soft

whereas if i talk about diamonds

diamonds have are shiny

and they are used in uh jewelries they

have

greater refractive index as well

they are very hard that is why they are

used as

grille in grilling and glass cutting as

well

so these are different uses of diamond

and wafer and the properties of

according to this structure and bonding

i am going to share some other

questions with you guys now so you have

a much clearer idea of how to solve

some mcqs during your papers so let's

discuss

some practice examples here the first

one is this statement shows that

graphite and diamond they are different

forms of the element carbon so you have

to tell that graphite and diamond

they are of the same element carbon how

are we going to get it

how are we going to know that they are

from the same element part

and they are only the different forms

now let's read the

statements the first one is both

graphite and diamond they have giant

molecules such

as complete combustion of equal masses

of graphite

so see first one is that they have

giant molecular structures time

molecular structures doesn't go anything

with

the same element being or the same

element carbon

graphite and complete combustion of

electrical masses are graphite and

produces equal masses of carbon dioxide

and no other products and

now let's see over here graphite and

diamond they are both

formed from carbon and when they are

going to be when anything made up of

carbon is going to become busted

and it's going to go through the process

of combustion it's going to produce

carbon dioxide and you see

that they have given you a hint that it

is not producing any other product and

it's not producing any other product

that

means that this element this substance

has to be from the same element part

right so the first one was wrong but the

second one is going to be correct

now we have the third one third one is

that it has both has different setting

points this doesn't

go with anything like they have the same

element card it doesn't do anything like

that

graphite conducts electricity whereas

now see these are the different

properties but they don't

go with being the same element card so

only uh

the statement which is correct is going

to be b

now which is a compound with air carbon

oxygen or steam carbon is an element as

we know

oxygen is molecule

right steam is h2o

a compound

molecular compound and air is a mixture

of gases so which one is a compound

coming in my next one

now here this statement is showing and

explains why

magnesium oxide has a very high melting

point

so magnesium oxide the first statement

states

magnesium atoms and oxygen atoms they

are joined by strong coconut points now

see

melting point and boiling point is all

related to the bonding

of the substance or of the

molecule so it depends on all of the

structure

if if it has stronger bonding then that

means

it has a high melting in one point

so this always has to do with something

with a

stronger bonding means

increased melting point and

boiling so

the second one is the crystal lattice of

magnesium oxide it resembles that of the

this doesn't have to do with anything

with the bonding

now uh and even the magnesium oxide ngo

crystal lattice is not at all resemble

the diamonds this is going to be wrong

the magnesium ions they are strongly

attracted to the oxide ions

no um the reaction between

uh the magnesium and oxygen is strongly

exothermic does not have to do anything

so it's always going to be a because we

are always concerned with the bonding

in which pair of the substances

does each so each means both

of the substances they have a giant

molecular structure

now see over here diamond is a giant

molecule structure iodine is not

sand silica and diamond both are giant

molecular structures both are correct

iodine and mutant both are not at all

they both are simple molecules

methane is a simple molecular structure

and silica is a

giant molecule structure so both in

which are correct it's only an

atp so which material has the

highest melting point now highest metal

point is always concerned with the

body now if i tell you this that ionic

bonds they

are always stronger

than covalent bonds

so

they're melting melting points is are

also going to be

more energy will be required to break

them down so it's going to be much more

higher which one is a

ionic substance then ammonia no methane

no

water no they all are formed by covalent

bonding and i will share

this more in my next two lectures so

sodium chloride nacl

is an ionic substance and i will share

more about ionic and covalent substances

in my next few lectures so this one has

a high spending point because ionic

substances have

um they have stronger bonds as compared

to covalent

in in case it is a giant coconut

substance so no one

over here was a giant problem substance

so

nacl has giant lettuce ionic lattice

that is fine this one is going to be

there

i will share some more um uh

things differently with the ionic

covalent and different pointing we are

going to cover different

types of bonding in my next few lectures

so

until then

thank you so much if you guys have any

other questions please comment down on

this video below if you have any queries

and i will reply to them if you have any

other questions and you are practicing

any more questions from your passwords

you can even ask me uh in the comments

below and i will reply to them inshallah

please be

stay tuned and stay with us and please

give us some

comments if you like them if you have

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us

let us know thank you so much happy

learning