Lesson video

Hello, I'm Mrs. Adcock and welcome to today's lesson on alcohols.

We are going to be looking at what are alcohols, some of the reactions of alcohols, and thinking about two different ways that we can make the alcohol ethanol.

Today's lesson outcome is I can describe and explain properties and reactions of alcohols.

Some of the keywords that we will be using in today's lesson include alcohol, functional group, solvent, fermentation, and hydration.

Here, you can see each of those key words written in a sentence.

It would be a good idea to pause the video now and read through those sentences.

You might like to take some notes so that you can refer back to them later in the lesson if needed.

Today's lesson on alcohols is split into three main parts.

The first part of today's lesson is going to be an introduction to alcohols.

Then we're going to move on to look at the reactions of alcohols, and then finally, we'll finish by looking at two different ways that we can produce the alcohol ethanol.

Let's get started on an introduction to alcohols.

Alcohols are a homologous series of compounds that contain the OH functional group.

A functional group is the atoms or group of atoms that are responsible for the way that a compound reacts.

Here is a model of the simplest alcohol, so we can see this alcohol has only one carbon atom and it contains that OH functional group and alcohols react at their functional group.

We have a check for understanding now.

Which of the following functional groups is present in alcohols? Is it A, a carbon to carbon double bond, B, a carbon bonded to an oxygen with a double bond, or is it C, an OH group? The correct answer is C.

So the functional group in alcohols is an OH group.

The names of alcohols have the suffix ol.

The first four alcohols in the alcohol homologous series are the longest carbon chain in this alcohol is one carbon long and therefore, it has the prefix meth.

It is an alcohol, so it has the suffix ol.

So we can see the name of this alcohol is methanol and we have the structural formula written there, which is CH3OH.

Here we have ethanol.

Ethanol has a carbon chain of two carbons and it has the OH functional group, and we can see we have the structural formula written there, which is CH3CH2OH.

The structural formula shows the arrangement of atoms in the molecule.

So our first two alcohols in the alcohol homologous series are methanol, then ethanol, then we have an alcohol with three carbon atoms. This is propanol, and you can see the structural formula there for propanol is CH3CH2CH2OH.

and the fourth alcohol in the alcohol homologous series is butanol.

So all our alcohols end in ol.

And the structural formula for butanol is CH3CH2CH2CH2 and the OH.

And then the OH.

Time for another check for understanding.

The image shows a molecule of A, methanol, B, ethanol, C, propanol, or D, butanol.

All of the options are alcohols because our molecule contains that OH functional group.

Check the number of carbon atoms that are in the longest chain of this alcohol and see if you can work out what its name is.

The correct answer is B, ethanol.

Well done if you chose B.

Methanol would be an alcohol that only had one carbon atom.

Propanol, the longest chain would be three carbon atoms, and in butanol, we would have a chain that's four carbon atoms long.

The boiling point of an alcohol is higher than the alkane with the same number of carbon atoms. Remember, the boiling point is the temperature where we have a change of state from the liquid state to the gas state.

If we look at this table here, we can see the boiling points of alkanes and the boiling points of alcohols.

And they've been matched up so that we have alkanes and alcohols with the same number of carbon atoms in the same row.

Methane has a boiling point of negative 164 degrees Celsius, whereas methanol, which has the same number of carbon atoms is an alcohol and it has a higher boiling point.

So the boiling point is 65 degrees Celsius.

We can see this pattern repeated throughout the table.

Ethane is an alkane that contains two carbon atoms, and then we have ethanol, which is an alcohol with two carbon atoms, and the boiling point of ethane is negative 89 degrees Celsius, whereas the alcohol ethanol has a higher boiling point of 78 degrees Celsius.

Propane has a boiling point of negative 42, and again, the alcohol which has the same number of carbon atoms would be propanol, and this has a higher boiling point of 97 degrees Celsius.

Again, we can see this pattern in butane and butanol.

To summarise, alcohols have a higher boiling point than alkanes with the same number of carbon atoms. Why do alcohols have a higher boiling point then than the alkane with the same number of carbon atoms? Alcohols are held together by stronger intermolecular forces and therefore, they require more energy to overcome these intermolecular forces, which is why they have higher boiling points.

We have a question here.

The boiling point of methane is negative 164 degrees Celsius.

The boiling point of methanol will be A, higher than methane, B, the same as methane or C, lower than methane.

The correct answer is A, higher than methane.

Methanol will have a higher boiling point than methane because alcohols have higher boiling points than the alkane with the same number of carbon atom.

Well done if you choose option A.

Time for our first practise task of today's lesson, and you need to complete the table shown below.

In the top row, you need to fill in the name of the alcohols.

In the second row, you need to fill in the molecular formula.

Now, be careful here because the question is about molecular formula.

Earlier on, we saw the structural formula, so this time, we are just going to show the number of atoms of each element that are present in the molecule, and you can see an example there for you of C2H6O.

For the final row, you need to show the displayed formula where you will show all of the covalent bonds present in those molecules.

Pause the video now and have a go at answering this question.

Then we'll go over the answers in a moment when you're ready.

Just before we go over the answers to question one, we're gonna have a go at question two.

Question two, use the information in the table and your own knowledge to estimate the boiling point of pentanol.

Pentol is an alcohol that has a carbon chain of five carbon atoms. Pause the video now, have a go at answering this question and then we'll go over the answers to question one and two.

Question one.

First of all, we're gonna look at methanol.

The molecular formula for methanol is CH4O and the displayed formula should look like that molecule there.

The next column is ethanol because we have two carbon atoms in this alcohol.

And the displayed formula will show those two carbon atoms and the OH functional group.

Then you should have shown the remaining hydrogen atoms ensuring that each of your carbon atoms has formed four covalent bonds.

Propanol has the molecular formula C3H8O.

Well done if you got that one right and the displayed formula is shown there for you.

We've got three carbon atoms, each carbon atom forms four covalent bonds, and we've got our OH group.

In the final column, we have butanol and the molecular formula for butanol is C4H10O.

Well done if you've got all of those correct.

You've clearly understood the work we've done on alcohol so far.

Question two, you needed to estimate the boiling point of pentanol.

The boiling point of pentanol is 137 degrees Celsius.

Hopefully, you've put any number between 130 and 145 degrees Celsius.

Now, how would you have worked out your answer? Hopefully you will have used the information about alkanes, and we see that pentane has a boiling point of 36 degrees Celsius, so we would expect pentol to have a higher boiling point than 36.

And then if we look down the alcohol column, we can see that as we go from propanol to butanol and then onto penal that that boiling point is increasing with the longer carbon chain length.

Well done if you answered that question correctly.

You have worked really hard in the first part of today's lesson.

We are now ready to move on to the second part of our lesson on reactions of alcohols.

Alcohols can react at their functional group, which is the OH group, and they can react here with sodium.

When alcohols react with sodium, they produce a salt and hydrogen gas.

And the word equation for this reaction is alcohol plus sodium, and remember, sodium is a metal in group one.

Alcohol and sodium react together to produce a salt and hydrogen gas.

Here, we can see an alcohol and sodium reacting together, and those bubbles hopefully you've realised, are bubbles of hydrogen gas.

An example of an alcohol reacting with sodium is methanol reacting with sodium.

And when methanol reacts with sodium, we form the salt, sodium meth oxide and hydrogen gas.

Here, you can see a balanced symbol equation for that reaction.

Time for another question.

Which of the following gases are formed when alcohols react to sodium? Is it A, oxygen B, carbon dioxide, or C, hydrogen? The correct answer is C, hydrogen.

So when alcohols react with sodium, we produce a salt and hydrogen gas.

Well done if you got that one correct.

You clearly focused well on the previous slide.

Alcohols can also undergo complete combustion, and when they do this, they release large amounts of energy.

You may have seen alcohols undergoing combustion reactions before when you've seen alcohol burning on a Christmas pudding.

There is an image there showing the alcohol combusting on a Christmas padding.

When alcohols combust in a plentiful supply of oxygen, so when they undergo complete combustion, they produce carbon dioxide and water.

And the complete combustion of ethanol, so an alcohol, is shown below.

We have ethanol reacting with oxygen to produce carbon oxide and water.

Underneath, you can see the balanced symbol equation for this.

We have C2H5OH, that's ethanol that reacts with three molecules of oxygen, and they react to produce two molecules of carbon dioxide and three molecules of water.

The complete combustion of alcohols actually requires less oxygen than the complete combustion of an equivalent alkane.

For example, propanol is an alcohol, and when that reacts with oxygen, it will produce carbon dioxide and water.

We can see the balanced symbol equation for that reaction shown.

The complete combustion of propanol requires nine molecules of oxygen for every two molecules of propanol that burn.

However, when we have an a cane such as propane and this reacts with oxygen, again, it will produce carbon dioxide and water because this is a complete combustion reaction.

There, we can see the balanced symbol equation for this reaction, and you may have noticed that the complete combustion of propane requires 10 molecules of oxygen for every two molecules of propane.

Overall, the complete combustion of propanol, so our alcohol, required less oxygen than the complete combustion of our alkane propane.

We can see those two equations lined up there alongside each other, and the propanol required nine molecules of oxygen, whereas the propane required 10 oxygen molecules.

Let's have a go at this question.

Alcohols require more oxygen than an equivalent alkane to combust completely.

Is that statement true or false? That statement is false.

Hopefully you worked that out.

Now, can you justify your answer? Is it A, alcohols require less oxygen than an equivalent alkane to combust completely, or is it B, alcohols require the same amount of oxygen as an equivalent alkane to combust completely? The correct answer is A.

So alcohols require less oxygen than an equivalent alkane to combust completely.

Well done if you've got that question correct.

Here's another question to have a go at.

Which of the following are the products of the complete combustion of alcohols? A, carbon dioxide and hydrogen, B, carbon dioxide and water, or C, carbon dioxide and salt? The correct answer is B, carbon dioxide and water are the products of the complete combustion of alcohols.

Well done if you got that question correct.

You have clearly understood the work on the reactions of alcohols very well.

We're going to look at another reaction of alcohols here.

Alcohols can be oxidised to form carboxylic acids.

Oxidising agents cause oxidation reactions to take place.

And the oxidation of ethanol is shown below.

We have a molecule of ethanol, which is an alcohol, and then we have an oxidising agent, and the alcohol will be oxidised to a carboxylic acid.

We can see a carboxylic acid shown here.

It contains two carbon atoms still, but the OH group has been oxidised to form that COOH functional group that we have present in carboxylic acids.

Let's see if we can remember what we've just learned.

When alcohols are oxidised by oxidising agents, they produce A, alkanes, B, alkenes, C, carboxylic acids or D, esters.

The correct answer is C, carboxylic acids.

When alcohols are oxidised by oxidising agents, they produce carboxylic acids.

Well done if you chose option C.

Time for another practise task, you've got two questions to have a go at here.

Question one, state the product or products of the following reactions.

You've got an alcohol reacting with sodium, ethanol reacting with sodium, the oxidation of methanol, and propanol reacting with an oxidising agent.

Then for question two, you need to write word equations for the complete combustion of ethanol and butanol.

You've got a lot to get on with there, so if you pause the video, have a go at answering those two questions and then come back when you're ready to go over the answers.

Question one, state the product or products of the following reactions.

When an alcohol reacts with sodium, it will produce a salt and hydrogen.

Well done if you remembered those.

B, ethanol reacting with sodium.

Here, we have got a named alcohol, so we need to name that salt, and the salt would be sodium ethoxide.

So we form sodium ethoxide and hydrogen.

The oxidation of methanol will produce a carboxylic acid and because we started with the alcohol methanol, our carboxylic acid would be methanoic acid.

Propanol reacting with an oxidising agent, this will again oxidise that propanol into a carboxylic acid, and the name of that carboxylic acid would be propanoic acid.

Well done if you got those correct in question one.

Question two, we needed to write word equations for the complete combustion of two alcohols.

We have ethanol plus oxygen and they will react together to produce carbon dioxide and water, and in B, we had butanol and that will react with oxygen.

Again, it fully reacts to produce carbon dioxide and water.

Again, well done if you got those questions correct.

We have looked at an introduction to alcohols and we've seen some of the ways that alcohols can react.

Now we are going to move on to the final part of our lesson on how we can produce ethanol.

Alcohols have many uses.

Short chain alcohols easily combust, so can be used as fuels, and we've got an image there showing how alcohols can be used in fuels because if you look carefully on that second pump, the one next to the diesel pump, we can see it says E10 on it, and you may have noticed this when you've visited a petrol station yourselves.

E10 means it contains 10% renewable ethanol.

We have an alcohol being used as a fuel.

Short chain alcohols are miscible in water and make good solvents.

A solvent is a liquid into which a solute dissolves.

So alcohols make good solvents.

Therefore, they are used in products such as medicines and perfumes.

Ethanol is an alcohol that is used in alcoholic drinks.

We've got an image there showing some wine, but ethanol is also used in other alcoholic drinks such as beer.

Which of the following are uses of alcohols, A, as solvents, B, in alcoholic drinks, C, as fuels, D, in photosynthesis.

The correct answers are A, alcohols are used as solvents.

They're also used in alcoholic drinks.

We use the alcohol ethanol.

And also some alcohols can be used as fuels because they release energy when they undergo complete combustion.

Well done.

If you identified all three of those uses of alcohols.

Ethanol, and we can see the structural formula of ethanol there, C2H5OH, can be formed by the fermentation of glucose from crops.

Fermentation is a process that produces solutions of ethanol from sugars resulting from the anaerobic respiration of microorganisms. Fermentation therefore, not only requires glucose from crops, also yeast, our microorganisms, a warm temperature of about 30 degrees Celsius, and also anaerobic conditions.

And anaerobic means without oxygen.

During fermentation, glucose is converted into ethanol and carbon dioxide.

We can see this shown here in the wood and symbol equation.

We have glucose and by the process of fermentation, this is converted into ethanol.

That's our alcohol and carbon dioxide.

The formula of glucose is C6H1206.

This forms two molecules of ethanol, which has the formula C2H5OH and two molecules of carbon dioxide.

There we can see the ethanol that's being produced.

Ethanol can also be formed by reacting ethene, that's an alkane with steam.

And the processing of crude oil provides as with alkenes such as ethene.

Ethene and steam react together under high temperature and pressure in the presence of an acid catalyst.

The reaction is et ethene plus steam.

We need high temperature and pressure and an acid catalyst.

And ethene and steam will react together to produce ethanol.

The formula for et ethene is C2H4, That reacts with steam, H2O, and that forms are ethanol C2H5OH.

There, we can see our ethanol that's been produced.

The first way we looked at was the fermentation of glucose, but we can also make ethanol from processing crude oil to produce et ethene and then reacting that et ethene with steam.

This is an example of a hydration reaction.

Hydration reactions involve the addition of water.

In this case, we have an alkene that has a carbon-carbon double bond that opens up, and then we have the addition of the hydrogen and the OH from water to form our ethanol.

Which of the following methods can we use to produce ethanol? A, combustion of ethane B, hydration of ethene, C, fermentation of glucose.

Choose any answers that you think are correct.

There are two methods that we've looked at to produce ethanol.

They are the hydration of ethene.

And remember, hydration means the addition of water, and fermentation of glucose.

So well done if you identified both of those answers.

Some of the advantages and disadvantages of making ethanol by the fermentation of glucose are: Advantages, glucose is from a renewable source.

We can keep planting more crops to get our glucose.

The process is carbon neutral because even though the fermentation of glucose produces carbon dioxide, when our crops are growing, they will photosynthesize and remove carbon dioxide from the atmosphere.

So overall, this process is considered carbon neutral.

It is a batch process.

This means that you make things in separate stages rather than continually making the product.

Batch processes generally require cheaper equipment.

The disadvantages of fermentation that it requires large areas of land to grow those crops.

The process is slow and also it produces an impure product, so we are then going to need to purify our product.

There are also advantages and disadvantages of making ethanol by the hydration of ethene.

So let's look at some of those now.

The advantages of this method are that the process is fast and that it produces a very pure product of ethanol.

It's a continuous process and therefore, it has lower labour costs.

Disadvantages though are that ethene comes from crude oil, and crude oil is a non-renewable resource.

This means that it is being used at a faster rate than it is formed.

Energy costs are high because of the high temperature and pressure that are required for this process, and also linked with that, the equipment is very expensive.

Time for another check for understanding.

Which of the following is a disadvantage of producing ethanol by the fermentation of glucose? Is it A, the reactants are non-renewable, B, it is a slow process, C, the energy costs are high to reach high temperatures, and D, the equipment to achieve a high pressure is expensive.

We are looking for any options that are disadvantages of producing ethanol by the fermentation of glucose.

The correct answer is B.

It is a slow process.

Options A, C and D all refer to disadvantages of producing ethanol by the hydration of ethene.

For our final practise task of today's lesson.

What you need to do here is evaluate the advantages and disadvantages of producing ethanol by the hydration of ethene.

So you're just thinking about that one method and see if you can try to list as many advantages and disadvantages as you can remember.

Pause the video now, have a go at answering this question, then come back when you're ready to go over the answers.

Your answer may include the following ideas.

The advantages of producing ethanol by the hydration of ethene are the processes fast, it produces a very pure product.

The process is a continuous one, and that lowers labour costs.

The disadvantages are ethene is produced from processing crude oil, which is a non-renewable resource.

High temperatures are needed, which require large amounts of energy to be used, so we'd have high energy costs.

And high pressures are needed, which require expensive specialist equipment to be used to carry out the reaction.

Well done if you included lots of those advantages and disadvantages in your answer.

It would be a good idea to pause the video now and make a note of any that you had missed from your answer.

We have reached the end of today's lesson on alcohols.

Let's just summarise some of the key points from today's lesson.

Alcohols can react at their functional group and their functional group is the OH atoms. And they can react here with sodium, oxygen, or an oxidising agent.

Alcohols need less oxygen than equivalent alkanes in order to burn completely.

Alcohols are good solvents, which also mix with water.

The boiling point of ethanol is much higher than the boiling point of ethane.

Ethanol can be formed via the fermentation of glucose, which is renewable or via the hydration of ethene, which comes from a non-renewable source.

You've worked really hard throughout today's lesson, so well done.

I've enjoyed the lesson.

I hope you have too, and I hope you're able to join me for another lesson soon.