Hello, my name's Mrs. Niven and today we're going to be talking about simple distillation as part of our topic on separation techniques.

And what we will learn in today's lesson will help us to answer that big question of how can we explain how substances behave.

Now you may be familiar with this idea of distillation because of what you might have heard outside of the classroom, things like a distillery or something that's been distilled.

What we're gonna learn in today's lesson though will help us to understand how we might be able to separate a solution but keep the solvent rather than the solute.

So by the end of today's lesson, you should be a little more comfortable talking about how distillation occurs and describing how we can separate a solution to recover a liquid from it.

Now we'll be using some keywords throughout this lesson, and those include distillation, condensation, delivery tube, condenser, and distillate.

The definitions for these keywords are used on the next slide and in sentence form.

And you may wish to pause the video here so that you can read through them or maybe jot down a quick note of what they mean so you can refer back to them later in the lesson.

So we'll be looking at two main things in today's lesson.

Firstly, we'll look at how we can describe what happens during distillation and then we'll move on to look more closely at the equipment used for distillation to take place effectively.

So let's get started by looking at how we can describe what happens during distillation.

So one of the most important features of distillation is this understanding that pure substances have unique boiling points and so they're going to evaporate and then boil at very specific temperatures.

So we have an example here of mixable liquids of water and ethanol that have mixed together into that beaker.

Water would boil at 100 degrees Celsius, but ethanol would boil at 78 degrees Celsius.

And if we look at another mixture, here we've got ink and water.

The water would boil at 100 degrees Celsius because it's a pure substance and it doesn't matter what it's mixed with, it's boiling point will stay the same, 100 degrees.

The inks though are usually made up of several different substances, and an ink could boil anywhere between 150 and 290 degrees Celsius, depending on the different mixture of substances within that particular ink.

So it doesn't matter what substances have been mixed together, the boiling points will stay the same for that particular pure substance.

So if we were to take one of our mixtures and heat it, what we would find is that the substance with the lower boiling point is going to change from the liquid state into the gas state first.

So it would boil first if it has the lower boiling point.

Now if we were to heat a mixture to separate a liquid from it, once that substance has boiled, changed from the liquid state into the gas state, it's essentially lost into the surroundings.

It's gonna mix with the air in the surroundings.

So by boiling this mixture as we can see here on the beaker, that is great, it separated off that lower boiling point substance, but I can't collect it anymore.

It's mixed with the air now and I don't know where it's gone.

So let's pause here quickly for a check on your understanding of boiling points.

What I'd like you to do is to use the information provided in the table to decide which of the substances would boil first if they were all mixed together.

Well done if you chose ethanol.

Ethanol is the correct answer, because when we look at the boiling points of all of the substances listed, it has the lowest boiling point, the smaller number.

So well done if you managed to choose ethanol.

So we know that if we apply heat to a mixture containing liquids, the lower boiling point liquid will be boiled first, but it's lost to the surroundings.

But if we use a different separation technique, we might be able to keep that boiled liquid and isolate it somewhere else.

And that's where distillation comes in.

It is a combination of processes that allow us to separate and isolate and keep a liquid from a mixture.

So it does that by using boiling and then condensation to remove and isolate that liquid.

So how does it work? There are three essential steps that take place in distillation.

The first one that takes place is that you have to actually heat your mixture.

We need to boil off that lower boiling point substance first.

So we're gonna do that really gently and really carefully to ensure that only one liquid is boiling within our mixture.

The next thing that needs to happen then is that we're going to use a delivery tube to move the now gas, because it's boiled, from one place to another.

And that's how we remember what a delivery tube is, because just like a delivery van might bring a package from one place to another, the delivery tube is taking our gas from where it was boiled in our mixture to another location.

What that delivery tube is doing is it's bringing that gas from our mixture into another container.

And as it does that, that gas that's travelling through the delivery tube is condensing, it's cooling back down into that liquid state.

So rather than the gas being lost into the surroundings, that gas is cooling back into a liquid that we can more easily contain within a desired container.

Let's stop here for another quick check.

Now, I mentioned in my description of distillation that two processes take place during that separation technique, but which two processes are they? You may wish to pause the video here so you can have a think, maybe chat over your ideas with the people next to you and then come back when you're ready to check your answer.

Well done if you said D, the answer is boiling and condensation.

Melting refers to something changing from the solid state into the liquid state.

And at no point during distillation are we talking about changing a solid state.

So very well done if you managed to choose D, boiling and condensation.

Time for our first task.

What I'd like you to do now is to use the words from the box to complete this summary paragraph about how distillation takes place.

You may wish to pause the video here so you can have a go, maybe have a chat with your neighbours to see if you agree on the words to choose, and then come back when you are ready to check your answers.

Okay, let's see how you got on.

Now, if you chose the words correctly to fill in the blanks, your summary should read like this.

Distillation is a separation technique.

A mixture is heated until one substance in it boils, changing to the gas state.

This gas substance is less dense than the mixture, so it rises into a delivery tube, where it is transferred to another container.

As the gaseous substance travels away from the heat source, it cools and condenses back into the liquid state.

Now that was a tricky paragraph to complete because you were given so many words to choose from.

So very well done if you managed to get all of those correct.

If you did manage to get a few incorrect, make sure that you've gone back to correct them.

And if you left some blank because you weren't sure, again, make sure you go back and fill them in because this is a great example of summarising a process of separation.

And I would also recommend whenever you have a summary statement like this is that you go back and perhaps highlight the words that you have chosen and put in that are correct so that they kind of ping out at you when you read through it later perhaps if you're revising.

So well done on a tricky first task.

So for the next part of this task, what I'd like you to do is consider this setup that is shown for distillation, and the mixture that we're using here is a salt solution.

What I'd like you to do is to think about what is the name and the state of matter of the substance that's going to be found at position X, and the same for position Y.

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

Okay, let's see how you got on.

Now, the key to being able to answer these questions is to realise that when we're talking about a salt solution, what we actually have here is salt being dissolved in a solvent, and the solvent is most likely water.

So when we apply heat to this salt solution, it's the water that is likely to boil first.

So when we get to position X, it's going to be water that is the name of the substance found there, and its state of matter will be the gas state.

So you could have said water in a gas state, or you could have even just said steam as referencing water in the gas state.

Now when we move on to position Y then, we are cooling down the gas that was travelling through that delivery tube.

And what we have here still is water, but this time now it's in the liquid state and you can see that from, kind of, you can see the little droplets of water that are being pushed into that test tube at position Y.

The key here to realise is that we have water that's turning into the gas state and it stays as water, it's just changing its state of matter as it moves into the Y state.

Now that we're feeling a little bit more confident describing what happens during distillation, let's take a closer look at the equipment that's actually used for distillation to take place.

Now we can see from the image here that some very specialist equipment is used for the better separation of our solutions.

And when we're talking about mixable liquids in our solution, rather than say sand and water and just wanting to keep the water off it, this kind of equipment is really important and they each have a specific job to do.

So let's take a closer look at these specialist apparatus that's used in distillation.

Now to help us keep clear that specialist equipment as we build it up, I'm going to introduce the parts of this equipment one part at a time.

So the very first thing we're gonna look at is this bit, it's the round-bottom flask.

It's called a flask because it's containing things like a conical flask, but like a conical flask, its name tells us the shape of it.

So it's a round-bottom flask, and we use these in our specialist distillation because it's able to heat the mixture that is in it a bit more evenly.

The other thing that we have in this particular part of the setup is we have a thermometer that is placed here.

And what that's doing is it's monitoring the temperature of the gas that's forming.

It is keeping track of the boiling point for the substance that is turning from the liquid state into the gas state.

And the position of the bulb of that thermometer is actually really important.

We can see a closeup view here that the bulb is just below the side arm bit that's sloping downwards in our diagram so that we can take the temperature of the gas just before it enters into the next piece of equipment in our setup.

So the next piece in our setup is probably the most important piece of apparatus in distillation, and that is the condenser.

And that's because this is the position where the gas substance will be condensed back into a liquid, okay? Now a condenser is essentially a tube that's surrounded by a cold layer, and it's usually cold water that's being pushed through it.

Now you'll probably see pictures of distillation condensers in lots of different ways.

Most commonly in the laboratory at school you might see something called the Liebig condenser, which is quite straight.

And you might even see on display on the side potentially a Graham condenser, which again shows that inner tubing, which is curlicued here.

And then the straight part of the tube, you can just see the reflections of on the left hand side of that right hand picture is where that cold layer of water will be found.

Now it doesn't matter if you are using one of these straight condensers or if you're using one of the curlicue Graham condensers.

Essentially the inner tubing of our condenser is known as a cold corridor.

And we can see that here in the circled bit of our diagram here on the right.

Now it's kept cold because it is surrounded by essentially a cold water jacket.

How that happens is that we can see that there are two connection points on our condenser, and the bottom one is where we would attach some tubing to that bottom connection point of our condenser.

And the other end of that tubing would be connected to a cold water tap.

When you turn that tap on, the cold water then will rush through the tubing and into the condenser, and the pressure of that water will then push up through the condenser all the way to that top outlet where the water then would be able to come out, and to make sure we don't make a mess, we'd attach tubing to that connection point, and then the other end of the tubing would probably go into a sink and down the drain.

So the key to remember though with this condenser is that we obviously have this cold inner tubing that is surrounded by cold water for the outer part of that tubing.

But the key point here is that the gas that's travelling through that cold corridor does not mix with the water that is enveloping it, keeping it cool.

So now that we have heated our mixture in the round-bottom flask, we've monitored the boiling point with the thermometer, that gas then has entered into our condenser at the top and travelled through that cold corridor.

It has condensed back into a liquid.

We can see that in our diagram with the little blue droplets partway through our condenser.

It then will travel through a delivery tube that will help, like before, to deliver one substance from one area into another.

So this delivery tube is transporting that liquid that has condensed into a container where it's being collected.

Now, this condensed substance then that's being collected is mostly pure and it's referred to as the distillate.

So on our diagram, that pure liquid is the bit that's dripping at the bottom of that delivery tube and being collected in the beaker.

And we would call that the distillate.

And some of the keen ears and sights among you may have noticed that when we used filtration, the liquid that dripped through our filter paper and into our conical flask was known as the filtrate.

So the liquid collected from filtration is a filtrate, and the liquid that is collected from distillation is known as a distillate.

So possibly a way for you to help remember those two key terms. Now that we have a better understanding of the specialist equipment that's used in distillation and how they all work together, if you'd like to see it in action, why don't you hit that watch button below and you can watch a description and distillation taking place within that specialist equipment.

So the first thing we're gonna do when we do our distillation is to put our sample into the round-bottom flask.

And then when we set it up, this is what will look like.

So we have a tube running from a tap to the bottom of our condenser and then another tube from the top of the condenser that is going to be leading into the drain.

So when the water is turned on, it's not gonna spill all over the place.

So we turn the water on and we can see it start to fill from the bottom.

Now you'll notice that there are a lot of water going in, but there's air bubbles as well.

Those need to be removed so that you've got that lovely cold corridor now filling up with our condenser and so the water is left to run whilst we turn the heating mantle on.

Now a heating mantle is essentially an electric heater, so we can control the heat a little bit better than we might be with a Bunsen burner, and we can actually put the round-bottom flask within it.

Then our thermometer is set up so that it is just at the tip where the side arm is, and we can start to see that our mixture is starting to warm up.

We've got some condensation on the inside there, and we can see that the temperature has increased by about 10 degrees, so it's now about 30 degrees.

Now we can see that it's starting to boil with the bubbles forming.

So we know that the temperature's going up even further as it starts to heat a little bit more evenly in that mantle.

And we check our thermometer and we can see that it's now up around about 55 degrees and rising.

So now we're at about 100 degrees centigrade and we can see that there is now a gas that has gone into and has condensed down into our test tube and is pure.

Okay, let's pause here and have a quick check.

Which piece of equipment must be kept cool during distillation? Well done if you chose C, the condenser.

A round-bottom flask definitely wouldn't work because that's where the mixture is heated.

A thermometer simply monitors the temperature of the gas that's going through the equipment.

And we've never talked about a distiller.

I've never heard of a distiller, so it doesn't really exist, sorry.

So well done if you've managed to choose C, the condenser needs to be kept cool.

One way to remember that as well is cool starts with a C, and so does condenser.

Okay, let's try another check.

This one's a little bit trickier.

So we have a solution here that is being heated to 100 degrees Celsius.

What colour do you think the distillate should be shaded if you were being asked to colour the distillate in? Now, you may wish to pause the video here, have a chat with the people nearest you, and then come back when you're ready to check your answer.

Well done if you chose D.

There would be no colour for this particular distillation.

Now it says copper sulphate solution, which tends to be blue.

Now because it says solution, in my head, the first thing I'm thinking about is water being present and it's heated to 100 degrees Celsius.

And I know that what boils at 100 degrees Celsius is water, and I know that water has no colour.

So that was a really, really tricky check to get you to think a little bit.

Well done if you've managed to choose D.

Okay, let's move on now to the first part of the last task for today's lesson.

We've talked about a lot of different pieces of equipment and some key terminology.

What I'd like you to do now is to take a moment and try to match up each term with the correct definition or description.

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

Okay, let's see how you got on.

Now remember that a condenser needs to be kept cool.

So when I skim through all these definitions and descriptions, I see that the bottom one says a tube surrounded by a cooling layer, and that's exactly what a condenser is.

A delivery tube makes me think of delivery people, delivery vans, and I know that they're carrying packages from one place to another.

So a delivery tube must be doing the same.

They are transferring a substance from one container to another.

So that's gonna be the top definition and description.

A distillate is like a filtrate.

It's the liquid that's collected at the end of a separation process.

So the distillate is going to be that liquid that condenses from the gas state during distillation.

Now a round-bottom flask, if you remember, is being used because it's able to transfer heat evenly to its contents.

So that's gonna be the second description or definition, which means the thermometer then is what is monitoring the temperature throughout the distillation process.

That was a tricky one for some of those keywords.

Hopefully you were able to find some of those key flagged ideas that helps you to pick the correct one.

If you did struggle, it might be worth you having a look at those definitions and descriptions and maybe highlighting one of the key words that would've helped you to pick that correct description or definition for each of the key terms so that when you are looking back at your work, it might help you to remember them.

So well done though if you managed to get those correct.

Now, for the next part of this task, what I'd like you to do is to use the words that have been provided in the bullet points on the left to label the different parts of the distillation setup on the right.

And you might find it useful to refer back to part one of this task because we now have those matched up words and descriptions or definitions to help you.

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

Okay, let's go through the answers to this part of the task.

Now, rather than trying to label the diagram in the order that the terms were provided, I'm going to go through them in the order that you would come across those terms going through this distillation setup and actually performing distillation.

So we can start by heating our mixture, and that's done by holding the mixture in our round-bottom flask.

And then we are monitoring the temperature of the gas that is being produced as that substance with the lowest boiling point starts to boil.

And we're doing that with the thermometer.

Once that gas is pushed up through that container, it's going to then enter the condenser.

And remember, that's our cold corridor with a cold jacket, and that cold jacket is formed by pushing water in at the bottom and then having water come out at the top of our condenser.

So it's constantly refreshing that cold jacket with fresh cold water as we go through.

And then finally, the distillate is the liquid that is collected at the end.

So well done if you managed to get those in the correct place.

The most common mistakes with this is that the water in and out is in the wrong positions.

Just remember that we start at the bottom and we're pushing that water up and out of the condenser.

That might help you in the future.

But well done if you managed to get those correct.

So let's move on now to the last part of this task.

Now, distillation has actually been around and in use literally for hundreds of years.

There are images of distillation that go back to the 1600s, in fact.

Now Sam here has asked for your help to label a distillation diagram that is from the 1800s, and you have some key terms to use.

You've got four positions that have been outlined for you, and some other parts of the diagram have been labelled that might help you.

So maybe pause the video here and then come back when you're ready to check your answers.

Okay, so let's see how you got on.

Now, the diagram that I'm showing you here just shows the specific parts we were gonna look at and some of the labels already.

Now, if I go through and use the labels that were provided, the very first thing that we can see here is our mixture.

It's what's actually being heated by that fire below.

Then we have our delivery tube.

It's transporting whatever's being heated with that lowest boiling point up through the delivery tube and putting it into the container then on the right hand side.

Then I have a condenser, and this condenser looks very similar to the Graham condenser we looked at earlier with that curlicued tubing that's being surrounded by water and that cold jacket, which means then the liquid that is collected at the bottom is our distillate.

Very well done if you've managed to get those in the correct order.

Hopefully you found some of the previous tasks and the definitions to help you with this as you went along, but really well done trying to apply modern day understanding of distillation to some of the historical diagrams. So to finish up, let's summarise what we've learned in today's lesson.

Well, we've learned that a liquid can be separated from its solution by boiling it, but then we can quickly condense it if we want to save that liquid from being lost into the air and into the surroundings as it's heated.

Now, distillation works because one part of our solution will have a different boiling point than the other part.

So for instance, sand will have a far higher boiling point than water.

So we could actually distil off the water and keep it if we wanted.

Additionally, if we had say an ethanol and water mixture, the ethanol would have a lower boiling point and we'd be able to remove the ethanol and save it from that water and ethanol mixture.

It's because they have these very unique boiling points.

Now, a condenser is one of the most important parts of our distillation apparatus, and that's because it's able to create this cold corridor, this tubing that's kept cold by being surrounded by this cooler jacket of water.

And what that does is it helps to speed up the process of condensation so that as much of our gas substance is changed back into the liquid state before it then leaves the end of the condenser.

And then the liquid that is collected at the end of distillation tends to be pure, and we refer to that as the distillate.

I hope you had a good time learning with me today.

I certainly had a good time and I hope to see you again soon.