GCSE Chemistry - Addition Polymers & Polymerisation #56

Summary

This educational video explains the process of creating addition polymers from alkenes, focusing on the representation of monomers, repeating units, and polymers. It highlights the role of carbon-carbon double bonds in alkenes, which can break and form new bonds under the right conditions, leading to the formation of polymer chains. The video demonstrates how to draw monomers and polymers, emphasizing the importance of representing bonds correctly and using repeating units to simplify the depiction of long polymer chains. It also covers the naming of polymers by prefixing 'poly' to the monomer's name and briefly mentions the necessity of high pressure and a catalyst for addition polymerization reactions.

Takeaways

• 🔬 Alkenes have a carbon-carbon double bond, making them unsaturated and capable of undergoing polymerization reactions.
• 🧬 The double bond in alkenes can break, allowing the carbons to form new bonds with other molecules, leading to the creation of polymers.
• 📐 To represent polymerization, monomers are shown on one side and the resulting polymer on the other, but this can be simplified by showing only one monomer and one repeating unit.
• 🔑 The repeating unit is the group of atoms that are repeated throughout the polymer and match the atoms in the monomer.
• ✏️ When drawing monomers, bonds should be depicted facing up and down, while in repeating units, they should extend out to the sides through brackets.
• 🔑 The variable 'n' represents the number of monomers and, consequently, the number of repeating units in the polymer.
• 📝 The polymer is named by prefixing 'poly' to the monomer's name, with the monomer's name in brackets.
• 🔍 In the example of butane, the monomer is rearranged to clearly show the double bond and the groups attached to it, facilitating the depiction of the polymerization process.
• 🔄 The process of drawing butane for polymerization involves simplifying larger groups into shorthand notation and ensuring the correct bond orientation.
• 🔑 Addition polymerization reactions typically require high pressures and a catalyst, which may be indicated on the reaction arrow.

Q & A

What is the key feature of alkenes that allows them to form addition polymers?

The key feature of alkenes that allows them to form addition polymers is the presence of a carbon-carbon double bond, which can break and form new bonds with other molecules.

Why are alkenes referred to as unsaturated?

Alkenes are referred to as unsaturated because of the presence of the carbon-carbon double bond, which means they have fewer hydrogen atoms than their saturated counterparts.

How does the double bond in alkenes facilitate the formation of polymers?

The double bond in alkenes can break, allowing the carbon atoms to form new single bonds with other molecules, leading to the formation of long chains or polymers.

What is meant by the term 'monomers' in the context of polymer chemistry?

In polymer chemistry, 'monomers' refer to the small molecules that can join together to form a polymer through a process such as addition polymerization.

How are the repeating units of a polymer related to its monomers?

The repeating units of a polymer are the segments of the polymer chain that are repeated throughout its structure and contain the same group of atoms as the monomer.

What is the significance of the 'n' in a polymerization reaction equation?

The 'n' in a polymerization reaction equation represents the number of monomer units that have joined together to form the polymer, indicating the degree of polymerization.

How should the bonds of a monomer be drawn when representing a polymerization reaction?

The bonds of a monomer should be drawn facing up and down rather than out at angles to clearly show the carbon-carbon double bond and the groups attached to the carbons.

What is the purpose of drawing empty bonds on the repeating unit in a polymerization reaction?

Drawing empty bonds on the repeating unit indicates the potential for further bonding, showing how the monomers link together to form the polymer chain.

How is the name of a polymer derived from its monomer?

The name of a polymer is derived by placing the word 'poly' in front of the monomer's name, with the monomer's name in brackets, such as polyethylene from ethene.

What conditions are typically required for addition polymerization reactions?

Addition polymerization reactions typically require high pressures and a catalyst to proceed effectively.

Outlines

00:00

🔬 Understanding Alkenes and Polymerization

This paragraph introduces the concept of addition polymers made from alkenes. It explains that alkenes are unsaturated hydrocarbons due to the presence of a carbon-carbon double bond. The paragraph details how alkenes can undergo polymerization to form long-chain polymers when the double bonds break and form new bonds with other molecules. The focus is on how to represent this process diagrammatically, emphasizing the importance of showing monomers, repeating units, and the polymer itself. It also highlights the practicality of representing the reaction with a single monomer and repeating unit instead of hundreds of monomers. Key points include drawing bonds correctly and understanding the concept of repeating units, which are groups of atoms that are identical in both the monomer and the polymer.

05:02

📝 The Process of Drawing and Naming Polymers

The second paragraph delves into the actual process of drawing and naming polymers. It demonstrates how to represent a monomer, such as butane, in a format conducive to showing the polymerization process. The paragraph guides through the steps of rearranging atoms to highlight the double bond and simplifying groups for clarity. It then explains how to add brackets to indicate the repeating unit and how to denote the number of monomers involved with the variable 'n'. The paragraph concludes with the naming convention for polymers, which involves prefixing the monomer's name with 'poly'. Additionally, it mentions the necessity of high pressure and a catalyst for addition polymerization reactions, which are often depicted on the reaction arrow.

Keywords

💡Alkenes

Alkenes are a class of hydrocarbons that contain at least one carbon-carbon double bond. This double bond is what makes alkenes 'unsaturated', meaning they can undergo addition reactions. In the context of the video, alkenes are the starting materials, or monomers, for the creation of addition polymers. The video script uses ethene as an example of an alkene, highlighting its double bond between two carbon atoms.

💡Carbon-Carbon Double Bond

A carbon-carbon double bond is a covalent bond between two carbon atoms, consisting of four shared electrons. This bond is a key feature of alkenes and is crucial for the polymerization process described in the video. The double bond's ability to break and form new bonds allows alkenes to link together and form polymers.

💡Monomers

Monomers are the small molecules that can join together to form a polymer. In the video, ethene molecules serve as monomers, which, through a process of opening their double bonds, can connect to form a polymer. The script explains that monomers are represented in chemical equations with bonds facing up and down.

💡Polymers

Polymers are large molecules composed of repeating structural units derived from monomers. The video focuses on addition polymers, which are formed by the linking of alkenes through their double bonds. The script illustrates how multiple ethene molecules can combine to form a long polymer chain, which is the final product of the polymerization process.

💡Repeating Units

Repeating units, also known as monomer units, are the segments of a polymer that are repeated along its length. Each repeating unit is identical and corresponds to the structure of the original monomer. The video script explains that these units are represented in chemical equations with empty bonds pointing out to the left and right through the brackets.

💡Addition Polymerization

Addition polymerization is a type of polymerization reaction in which monomers with unsaturated bonds, like alkenes, add onto each other to form a polymer. The video script describes this process, showing how the double bonds in alkenes can be broken to allow the formation of new bonds with other monomers, leading to the creation of a polymer.

💡Ethene

Ethene, also known as ethylene, is a simple alkene with a carbon-carbon double bond between two carbon atoms. It is used in the video as a model compound to demonstrate the process of addition polymerization. The script shows how multiple ethene molecules can polymerize to form polyethylene.

💡Butane

Butane is a four-carbon alkene used in the video script as an example to illustrate the process of drawing and naming polymers. It has a double bond between the first two carbons, and the video explains how to represent its monomer and polymer forms, leading to the naming of the polymer as polybutane.

💡Polyethylene

Polyethylene is the polymer formed from the polymerization of ethene monomers. The video script mentions polyethylene as an example of an addition polymer, highlighting how the process of polymerization converts simple alkenes like ethene into useful materials.

💡Polymer Naming

The video script explains the naming convention for polymers, which involves prefixing the monomer's name with 'poly-'. This naming system is straightforward and indicates the polymer's origin from a specific monomer. For instance, the polymer derived from butane is named polybutane, following this naming convention.

💡Catalyst

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. In the context of the video, catalysts are necessary for the addition polymerization reactions to occur. The script mentions that these reactions require both high pressures and a catalyst, indicating the importance of catalysts in industrial polymer production.

Highlights

Introduction to making addition polymers using alkenes.

Explanation of alkenes as unsaturated hydrocarbons due to carbon-carbon double bonds.

Description of how double bonds in alkenes can break to form new bonds with other molecules.

Illustration of polymer formation from three ethene molecules.

Challenge of drawing polymers with hundreds of monomers and a proposed solution.

Introduction to the concept of repeating units in polymers.

Guidelines for drawing monomers with bonds facing up and down.

Instructions for drawing repeating units with empty bonds pointing left and right through brackets.

Explanation of 'n' representing the number of monomers and repeating units in a reaction.

Tutorial on writing an equation for the addition polymerization of a four-carbon alkene.

Step-by-step guide to redrawing butane to match the format of ethene for polymerization.

Technique for simplifying large groups in molecules using shorthand notation.

Importance of drawing bonds from carbon to carbon in the polymerization process.

Process of adding brackets and 'n' to represent the repeating unit in a polymerization reaction.

Method for naming polymers by prefixing 'poly' to the monomer's name.

Examples of naming polymers: polybutane, polyethylene, and polychloroethylene.

Mention of the requirement of high pressures and a catalyst for addition polymerization reactions.

Conclusion and appreciation for watching the video.

Transcripts

[Music]

in today's video we're going to look at

how we can make addition polymers

using alkenes

with a focus on how to draw the monomers

the repeating units and the polymers

the feature that makes a molecule an

alkene is the fact that it has a

carbon-carbon double bond

like we can see here between the two

carbon atoms in this ethene molecule

because of this double bond we say that

alkenes are unsaturated

and under the right conditions the

double bond can break into a single bond

which allows the two carbons to form new

bonds with something else

so if we had three ethene molecules

and all the double bonds opened up

then they'd be able to form new bonds

with each other

and so combine to form one long chain

which would then call a polymer

now one way to represent this reaction

would be like this

where we show all the ethene molecules

which are our monomers on the left

and draw out the entire polymer that

they form on the right

the problem with this technique though

is that these reactions can sometimes

involve hundreds of monomers

so to draw out all of them would take

forever

a better way to do it is like this

where we show a single monomer on the

left

and a single repeating units of our

polymer on the right

and when we say repeating units all we

mean is the group of atoms

that are repeated throughout the

polymer and contain exactly the same

group of atoms as i ran the monomer

so in this case two carbons and four

hydrogens

when it comes to writing out these

equations yourself there's a few points

that you need to remember

one is that you need to draw the bonds

of the monomer facing up and down rather

than out at angles

and on the repeating unit you need to

draw these empty bonds pointing out to

the left and right that go through the

brackets

the other important feature are the ends

which represent how many of the monomers

and thus how many repeating units

there are in the reaction

for example if n was 10

then that would mean that there were 10

ethene molecules on the left

and so the polymer would be 10 repeat

units long

to put all of this together let's try

and write an equation for the addition

polymerization of

which is this four carbon alkene

the first thing we need to do is redraw

the butane

so that it's in the same format as this

diagram of ethene that we just saw

to start we need to identify the double

bond

which is here between the first two

carbons

next we need to arrange all of these

atoms as separate groups

because they're the groups attached to

the carbons of our carbon-carbon double

bond

and if you look back at our ethene

example we need to place them directly

above and directly below the two double

bonded carbons

to do this for butane let's start with

our two double bonded carbons

and then we'll rearrange each of the

separate groups one by one so that it's

easy to follow along with what's

happening

this first hydrogen

needs to change from being shown

sticking out at an angle to being shown

like this

pointing straight up from the carbon

and we do exactly the same thing for

this hydrogen

so that it points straight down rather

than sticking out an angle

then this hydrogen over here is already

pointing straight down so we just redraw

it exactly the same way

finally for this big group on the right

we use a little trick and simplify it

before moving it about

to do this we just count up all the

carbons and hydrogens and write them out

in shorthand

so because there are two carbons and

five hydrogens we write this group as c2

h5

and then we just do exactly the same

things before and rewrite the group so

that it's directly above our double

bonded carbon

one thing to be aware of though is that

it's important that this bond is drawn

going from carbon to carbon

rather than to the h5 part

now that it's drawn in the right format

we can add the brackets and put the n in

front of it

next we can draw our reaction arrow and

then draw the other side of the equation

that shows the repeating unit

we draw pretty much exactly the same

thing

but notice that we've taken out the

double bond and instead put the carbon's

bonds out to the sides

extending through the brackets

and remember for a repeating unit the n

goes here on the bottom right just

outside the brackets

the last thing we need to cover is how

to name the polymers

which is actually really easy

because all we have to do is put the

word poly in front of the monomer's name

and put the monomer's name in brackets

so in our example here where we're

drawing the polymer of butane

the monomer is butane

and therefore the polymer is called

polybutane

or if we go back to the first example we

did the polymer would be called

polyethylene

or if we had this monomer which is

called chloroethene

we'd make the polymer polychloroethylene

the very last thing we need to mention

is that these addition polymerization

reactions

require high pressures

and a catalyst to work

so you might sometimes see pressure and

catalyst written on the reaction arrow

you don't have to put this on the arrow

yourself

but you might be asked for these two

conditions

anyway that's everything for this video

so hope that all made some sense

and cheers for making it through to the

end