Hello, my name's Mrs. (indistinct) and today we're going to be doing a distillation practical as part of our topic of separation techniques.

Now, you may be familiar with the idea of how distillation occurs from some of your previous learning, but what we do in today's lesson will help us to not only answer that big question of how can we explain how substances behave, but we'll also gain a better appreciation of the skills involved so that distillation can occur effectively and really appreciate as well how we can improve on those skills to make sure that as we go forward in our journey through science, we're able to carry out these techniques confidently and successfully.

So by the end of today's lesson, you'll not only be able to compare two different types of distillation, but you'll also be able to successfully carry out distillation to separate a mixture of miscible liquids.

Now, we'll be using some keywords throughout today's lesson, and these will include distillation, fraction, boiling and condensation.

The definitions for these keywords are given in sentence form on the next slide, and you may wish to pause the video here so you could read through them or to jot down some notes to refer to later on in the lesson.

So we'll start today's lesson out by looking at the differences between simple and fractional distillation before moving on to carry out the distillation practical itself.

So let's get started by looking at the differences between simple and fractional distillation.

One thing to understand about distillation is that as a separation technique, it can be used on many, many different types of materials.

For instance, on a large scale, we might be able to take polluted water, conduct distillation on it and end up with clean water that's safer for us to use.

Another large scale use of distillation might be on crude oil.

When that's performed, distillation is performed on crude oil, we get a lot of our fuels, things like jet fuel, petrol, diesel and things like that.

Now, distillation can also be used on a smaller scale.

For instance, you could perform it on plants in order to extract their essential oils.

So in this picture we've got lavender oil, but you could also use it on rose oil, things like that that are used in perfumes.

Some of you might be more familiar with it when talking about mash distilleries.

There's quite a few pictures that you might find online about these, but this is essentially the distillation that's used for extracting alcohols that are used in things like whiskeys, gins, stuff like that.

And more commonly though, in the laboratory, it's used in extracting specific ingredients that we might need in medicines from the mixtures that they're found in when they are produced in the first place.

Now, why do we care? Because the type of distillation that you use in order to extract that particular substance is gonna depend on the type of mixture that you start with.

Now, one type of distillation that we could use is called simple distillation.

And what we're doing is we are extracting just one liquid part from our mixture.

And some of the common mixtures we might use it on are things like sand and water, salt and water, ethanol and water.

But what you'll notice with each of these examples is that they're very simple mixtures.

It's simply two things that are mixed together, but we've got an insoluble solid in a solvent, a soluble solid in a solvent, and then we have two omissible liquids.

So we've got many different types of mixtures we could use this simple distillation on, but crucially, we're only removing one liquid part.

So we are only producing one distillate using simple distillation.

Fractional distillation on the other hand, is a type of distillation that is used where you are going to separate a mixture and actually produce multiple distillates.

So we can see that in our diagram here we have two different distillates that have been produced.

Now when that happens, what we tend to do is refer to each distillate as a fraction and just like in maths, it's a part of a hole that we've started from.

So we could talk about the blue fraction or the yellow fraction in our example here in the diagram.

So let's take a closer look at the difference between simple distillation and fractional distillation.

So simple distillation we said is going to be used when we want to separate a mixture of probably just two substances 'cause we're only gonna collect one distillate from it.

Fractional distillation could be used to separate a mixture where you have more than two substances and therefore the possibility of more than one distillate.

It can also be used if we want to separate substances that have very close boiling points.

So how does that work? Well, if we compare our two setups between the simple distillation and the fractional distillation, we can see there's only one part really that looks significantly different here and that's the bit that is attached directly between the round bottom flask there, the heat is being applied and our condenser where our gas is being condensed back into the liquid state.

What we have on the fractional distillation setup is a very tall column and we tend to refer to this as a fractionating column.

And what that does is it really forces, that separate stretches out the space that these gases need to be able to travel to, to stay in the gas state and actually separate off into that condenser.

So you can see that in that separating column, there's little lines along it.

And what you might find in carrying out distillation and using a fractionating column is that as the gas travels through it, it might condense on one of those pieces, move back down, and then it's not going to go into the condenser until more of that gas has actually reached its boiling point all the way up that far away from the heat source.

Now, we're gonna learn more about fractional distillation in another future lesson, but for now, hopefully this helps you to understand the differences between these two types of distillation.

Simple distillation is for very simple mixtures.

Fractional distillation is for more complex mixtures or those that contain substances with very close boiling points.

Let's take a moment to check and see how you're getting on understanding the difference between simple and fractional distillation.

True or false, simple distillation is best used for separating a mixture of three liquids? Well done if you said false, but which of these statements best supports your choice? You may wish to pause the video here so you can read them through fully and maybe talk it over with the person next to you and then come back when you're ready to check your answer.

Well done if you said A.

Simple distillation is best used for separating a mixture of two substances.

If you have two liquids with very close boiling points, it's better that you use fractional distillation.

Well done if you managed to get that correct.

Okay, let's move on to the first task of today's lesson.

What I'd like you to do is to consider each of these mixtures listed below and decide if simple or fractional distillation would be the better choice for separating those mixtures.

So not only are you choosing which distillation type to use, I want you to explain why you made that decision.

So I'm looking for because clause.

Now to help you with your decisions, I've included the boiling points for each of the substances in that mixture.

You may wish to pause the video here and then come back when you're ready to check your answers.

Okay, let's see how you got on.

For mixture A, which is made of water and sugar, I would've said simple distillation is probably the best type to use.

And that I would say is because there's only one liquid present.

You may have also said because there are only two substances in that mixture and that would also be correct.

For mixture B, which is made of water, ethanol and rose oil, fractional distillation would have been better to use.

And that's because we're trying to separate three different liquids and therefore we.

'Cause it's a more complicated mixture, we need the more complicated setup.

For C, we have acetone and petrol here.

Now simple distillation would be useful here.

Again, it's because we have two liquids.

So it is a simple mixture, but there's a large enough difference in the boiling point that we'd be able to successfully separate them.

For D, which is made of turpentine and jet fuel, fractional distillation would have been the better choice.

Now, that's because whilst we still only have two liquids present, it's quite a simple mixture because there's only three degrees Celsius between them in terms of their boiling point, we'd need that fractional distillation to separate out those substances more successfully.

The boiling points are simply too close together for us to use simple distillation effectively.

Very well done if you managed to choose the correct distillation technique and supremely well done if you managed to also include your reasons why.

For the next part of this task, I'd like you to help Jacob.

He's preparing for a camping expedition and he's really worried he might run out of drinking water.

So what I'd like you to do is help him to design a way that he could obtain clean water from muddy water and we need to use items that he'll be bringing with him on this expedition anyway.

So some of the things that he'll find in his pack, and it might be useful in your design is a camp stove.

He'll have a kettle and a straw, there'll be some elastic bands and a towel.

He'll also have some matches and a mug.

So what I would suggest you do is you're going to outline how you could use his items to heat the dirty water, collect the steam that would be produced, cool that steam, and then collect that condensed water that forms as the steam is cooling.

You may wish to pause the video here then, so you can talk it over with the people nearest you, jot down your ideas and then come back and we'll look through how you go on.

Now, I'm sure there's gonna be a large variety in the answers that people will have prepared and that will be down to the creativity of you amazing people and also the variety of equipment that's at your disposal.

Now, you may have included some of the following though in your answers.

So the first thing we needed to do was to heat that dirty water.

So I would've recommended collecting some of that muddy water in the kettle, using the matches to light the camp stove and then simply placing that kettle on the stove and heating it until the water boils.

Then we need to collect the steam that is produced as a result of heating that muddy water.

So I'd position the straw so that one end is in the neck of the kettle, so we're collecting that steam, but we also need to cool it.

So what I would do next then is probably wet that towel in some cold water and it's okay if it's muddy cold water as long as it's cold.

And then I'd wrap it around that straw and use the elastic bands to secure the towel to the straw and also hopefully the straw to the kettle neck.

And then finally, I need to collect that water that is condensing as it travels through the straw that's been wrapped in that cold towel.

So I will make sure that the other end of the straw is in the mug so that I can collect that water to drink later.

It's not an easy task, but I'm really, really glad that you guys had a go.

Very well done.

Now that we're feeling a little more comfortable talking about the differences between simple and fractional distillation and maybe how to go at designing our own simple distillation setup using some common equipment, let's look at moving onto the distillation practical itself.

Now, the thing to remember about distillation is that both boiling and condensation are occurring.

So boiling is taking place in this round bottom flask nearest to the heat source, and then condensation is taking place in the condenser as it moves away from that heat source.

So the first step in distillation is obviously boiling that mixture.

What I would always recommend is that we slowly boil it.

There is usually a temptation to just whack the heat up as high as you can 'cause that you think the distillation will happen better.

But if we slow down and very gently heat that mixture, we're gonna have far more controlled boiling of the liquids in that mixture.

And what that does is it helps to ensure that only one substance boils at a time and therefore we're only sending one gas into the condenser at a time.

So we are truly separating that mixture out and ensuring that the distillate that forms is as pure as possible.

Now the other thing we can do is to make sure that our condenser is kept cool so that we have far more effective condensation.

The diagram here shows what is referred to as a liebig condenser.

It's quite a straight condenser and the outlets both at the bottom and the top is where we might attach a cold water supply to it and allow it to travel around the outside of creating this kind of cool water jacket around that inner tubing and then the water would travel out the top outlet.

Not everybody has access to a condenser like this, so we might need to think of other ways to keep our condenser as cool as possible.

And the reason we wanna make sure that our condenser is kept cool is so that that makes sure that the gas that's travelling through it is able to change into the liquid state before it actually leaves the condenser.

It's not always possible to make sure that that condenser is stayed cool, so sometimes it's simply moving it away from the heat source.

But the idea is that we are trying to make sure the gas state turns back into the liquid state by the time that that substant reaches the end of the condenser.

Because if we are not able to do that, if the condenser's not cool enough, some of what would've become the distillate, the gas could actually simply leave that delivery tube and rather than being in the liquid form and simply drip into our container, it might still be in the gas state and which case it will simply mix with the air at the end of that delivery tube and then be lost to the surroundings.

So trying to keep that condenser as cool as possible is really important.

Let's stop here for a quick check.

We've got a mixture here that's being heated and it is composed of three different liquids and it's been really quickly heated to 150 degrees centigrade in a simple distillation setup.

And the boiling point for each of the liquids in that distillate is shown below.

So liquid X will boil at 70 degrees Celsius, Y will boil at 150 degrees Celsius and liquid Z will boil at 200 degrees Celsius.

What I'd like you to do with this information is to tell me what do you think will be collected in that distillate at the end? You may wish to pause the video here so you can discuss your answers with the people nearest you and then come back when you want to check your answer.

Now, this was a really tricky question, but very well done if you managed to choose C.

Both liquids X and liquid Y would be found in that distillate.

So more than one substance would be found in that distillate.

And the reason is we already know that liquid Y will boil at 150 degrees Celsius, so it's definitely gonna contain liquid Y.

Liquid Z will not be in that distillate because it hasn't boiled yet.

The temperature has not reached its boiling point of 200 degrees Celsius, but liquid X will also be there because it's boiling point is below 150 degrees Celsius.

So when its mixture is boiled to a particular temperature, especially in a simple distillation setup, if you're not keeping track of that boiling point very easily and carefully, then you could potentially have two substances in your distillate because X's boiling point is below that of 150 degrees.

It is also gonna be found in our distillate.

So an incredibly tricky question, very well done if you managed to choose at least liquid Y and supremely well done if you managed to say both X and Y would be found.

Okay, let's move on to the first part of our next task.

What we have here is a setup for distillation that some students are going to be using and they're discussing ways that they might be able to improve this setup.

What I'd like you to do is to discuss their suggestions and how they might or might not help to improve their distillation techniques.

So what we have is Aisha first of all is suggesting that they could swap the test tube rack for an ice bath, which is simply a beaker filled with ice and water.

Jun has said that they could turn the Bunsen burner up so the mixture gets hotter.

And then Sophia has suggested that they could wrap a cold cloth around the delivery tube.

So discuss their suggestions and thinking about how those might or might not help distillation to take place.

Pause the video here and come back when you're ready to check your answers.

All right, let's see how you got on.

Now if you remember, Aisha suggested swapping the test tube rack for an ice bath and Sophia suggested wrapping a cold cloth around the delivery tube.

Now, both of those suggestions of using an ice bath and a cold cloth would actually help cool the gas and cause condensation to occur, and that would help us to collect the liquid that is produced as part of our distillate.

June suggested possibly turning the Bunsen burner up to make sure that the mixture gets hotter.

The problem with this is that if you rapidly heat that mixture, you could actually cause two substances to reach their boiling point, and both of those substances might go into the delivery tube and be collected as part of the distillate.

So you wouldn't actually be separating anything.

You'd simply be turning most of your mixture into a gas and then collecting it as a liquid on the other side.

And the whole point of distillation is to separate things out.

So to do that, we need to make sure that we are heating our mixture gently and slowly to ensure only one substance enter the delivery tube at a time.

Now, that was a tricky, tricky task.

I hope you had some really good conversations and that you were kind of on the right track as we went through these answers.

Well done.

Okay, time for the final part of today's lesson.

What I'm gonna ask you to do is to use this picture as a guide to create a distillation setup and then you're going to use your setup to distil a sample of inky water.

Now there are a few parts of this picture that I want to draw to your attention.

You'll notice on the right hand side that the conical flask has a clamp around it, but we can't quite see what the clamp is attached to.

It is attached to a clamp stand using a boss, and that's just to help give your conical flask a little bit extra support so it doesn't tip over.

We can also see that our delivery tube is kept far enough away from the Bunsen burner so that it doesn't accidentally get heated as well.

We are keeping that nice and far away.

We can see as well that we have an ice bath that is on the left hand side of that picture, but the delivery tube wasn't quite long enough.

So if you need to, you might need to use some sort of support in order to raise that ice bath up a little bit.

Just make sure that you are doing it safely and that you get that set up double checked by an adult in the room before you get started to make sure that everything is being safely conducted.

Now, as you carry out this distillation practical then, what I'd like you to do is two things.

Think about what you notice about the colour of the mixture you are separating as the distillation proceeds.

What are you noticing about that? The other thing I want you to try to keep track of is what are some difficulties that you encounter as you try to carry out distillation? And if you did encounter any difficulties, how did you overcome them? What did you do that helped you to solve this issue you were having? So pause the video here, carry out your distillation and come back when you're ready to check your answers.

Now, if for some reason you do not have the equipment or are unable to actually perform the distillation, what you can do is click on the watch button below and see a demonstration of the setup that is shown in this picture to see how it's actually conducted.

So we've set up our inky mixture in a conical flask and placed it on top of a tripod and gauze, and I've been heating it with a Bunsen burner below and it's at boiling point.

We can see that because of the bubbles within the inky water mixture.

The conical flask is then given a little bit extra support by attaching it to a clamp and boss, which is then attached to a clamp stand that is out of picture.

Now, as the mixture boils, we can start to see little bubbles being pushed into the delivery tube just above where that clamp stand is attached.

And what that is, is actually the gas being pushed into that delivery tube.

And as that gas gets pushed further and further away from the heat source, we can see it condensing as it drips down into the other container, which in this case is a test tube which is inside an ice bath in a plastic beaker.

Welcome back.

Some of you may have decided to improve the condensation that might take place in your delivery tube by wrapping it in a cold wet towel.

But don't worry if you didn't, there should have been enough of a temperature difference as your gas travelled through that delivery tube for you to collect some distillate.

So let's go through the answers of the things I asked you to consider as you were carrying out distillation.

So the first question is, what did you notice about the colour of the mixture as that distillation proceeds? And with your inky water, what you should have seen is that the colour of the remaining mixture, so what's left in that conical flask should become darker or a much stronger colour as that water is distilled off.

So that colour of the result in that leftover mixture was becoming darker.

The other thing that I asked you to think about was any difficulties you may have encountered throughout this distillation process.

For some of.

There will be a wide variety of things that you would've come across, but also not just identifying the issues, but how did you overcome them? That's one of the hardest things to do in the lab sometimes I think, and it's really important in practical work for us to stop and consider, well, what did I do this time that I might be able to use next time? For some people it may have been actually setting up this distillation practical in the first place.

Trying to position materials in the right height location, particularly if you're using a clamp stand, might have been a little bit tricky.

You may have also found it difficult to control the heat with the Bunsen burner depending on the height of the flame of the Bunsen burner you're using, maybe the strength of that flame.

Did you use a light blue flame or did you use a strong roaring blue flame? I mean, some of the things you could have done if you did struggle with the heating process was to turn the flame down so you can actually control the height of your flame by the gas tap control.

You could have controlled the strength of that flame.

So if it's a roaring flame or a gentle flame, by turning the regulator on the bottom of your Bunsen burner, you could have even potentially pulled that Bunsen burner out from underneath the conical flask.

Now, the problem is if you did that whilst it would work to kind of cool down your mixture for a little bit, it creates what's called reduced pressure.

And what that would've done is if your delivery tube and in your container where you're collecting the distillate, if that delivery tube was right up against the bottom of that container, any distillate you'll have collected would've been sucked back up that delivery tube and you lose the distillate that you managed to produce.

So one of the things you could have done if that was an issue for you, is to just reposition your equipment so that the delivery tube doesn't touch the bottom of the container that you are collecting your distillate in.

So lots of different fiddly bits that you could play around with if you ever conduct distillation again in the future.

But I hope you had a really good time carrying out that practical.

It's one of my favourite ones.

And I think for a lot of people it's possibly the first time that they get to use so much different equipment, Bunsen burners.

And I like to see a little bit of a competition to see who can get the purest distillate.

So that's another challenge for you.

Can you think about what could you do to your distillate to test to see if it was pure? Any ideas? Check the boiling point.

Well done guys on a tricky task, but I hope you enjoyed it.

Well, we've had a really exciting lesson today, and I hope you've had a good time.

But let's summarise what we've learned today.

We've learned that simple distillation is a technique used to separate a mixture containing only two substances, and we're collecting one part of it and forming one distillate.

Fractional distillation, on the other hand, will separate mixtures with three or more substances in it, or it can be used to separate substances that have very similar boiling points within that mixture.

We also looked at how we can improve the distillation technique as it's carried out.

And we learned that if we heat that mixture slowly, we're gonna have far more controlled boiling of the individual parts of that mixture and ensuring just one gas is entering our condenser at a time.

We also learned that the condenser must be kept cool because if it warms up, condensation is less effective and that might lead to gas escaping into the surroundings.

And that's because it hasn't changed into the liquid state before it's left the condenser and turned into our distillate.

So looking at the different types of distillation that we could perform and then looking at how we can improve our technique as we carry out distillation.

I had a great time today.

I hope you did too, and I hope to see you again here soon.