GCSE Chemistry - Addition Polymers & Polymerisation #56
Summary
TLDRThis 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
🔬 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.
📝 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.
Mindmap
Keywords
💡Alkenes
💡Carbon-Carbon Double Bond
💡Monomers
💡Polymers
💡Repeating Units
💡Addition Polymerization
💡Ethene
💡Butane
💡Polyethylene
💡Polymer Naming
💡Catalyst
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
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