Hello, my name's Mrs. Nevin.

And today we're going to be talking about filtration as part of our topic on separating substances.

Now you may have some experience about filtration from your previous learning or even from home if you've ever done car mechanics or cooking.

But what we'll learn in today's lesson will help us to better understand filtration in a deeper level and also answer those big questions of how can we describe what substances are made of and also how can we explain how substances behave.

So by the end of today's lesson, you should be able to describe how to carry out filtration, but also explain how it works.

Now throughout the lesson, I'll be referring to some key terms. And those include component, filtration, residue, and filtrate.

Now the definitions for these keywords are in sentence form on the next slide.

And you may wish to pause the video here so you can read through them or perhaps jot a note of them down so that you can refer to them later in the lesson or later on in your learning.

So today's lesson is made up of two main parts.

The first is looking at performing filtration.

So we're looking at describing how it works and what kind of mixtures it would be used for.

And then we'll move on to look at explaining how filtration actually works, so using some better key terms to describe what's actually going on there, to really think of the nitty gritty aspects.

But let's get started by looking at how we perform filtration in the first place.

I said at the start that this lesson is part of the wider topic of separating substances.

And the first thing a chemist needs to think about when they are deciding which technique might be best to separate the particular substance is to look at the mixture that they are separating.

So as a reminder, a mixture is a material that contains two or more different substances that can be physically separated.

Now those different substances in a mixture that can be physically separated are referred to individually as a component.

So if we look at this mixture that we have here, we can see that we have a less dense, insoluble component that's floating at the top of the mixture, we have a liquid component, and then we can also see at the very bottom a more dense, insoluble component that has settled to the bottom of that container.

And the key point here is that all three of these components, the different parts that make up the entire mixture, could be physically separated.

Now my previous example showed two different insoluble substances.

So one of the things we could think about is the fact that an insoluble component's particle size could actually influence how it's separated from a mixture.

In this example here, I have some water and large marbles.

Now those large marbles are quite dense, and they have fallen to the bottom of my container.

But they're so large in fact that I could literally reach my hand in and individually remove them, so separating my mixture out into large marbles left on the table and the water left in the container.

If I looked at another insoluble component, this time I have small sand grains, I wouldn't be able to reach my hand in and pick out each individual sand grain.

One, it would be very, very lengthy.

And two, it's likely that I'd probably miss some of those particles, and therefore it wouldn't be fully separated.

One option I might have to separate that sand and water is linked very closely to the density of that component.

If the insoluble component is more dense, it's probably fallen to the bottom of that container.

And that's quite handy because I could use the technique of decanting.

Now decanting is simply taking your mixture and then very slowly pouring it out so that the top less dense layer is removed and then you're left with that more dense component left behind in that container.

Now the problem with this particular technique is that it doesn't fully separate the mixture.

We can see here in our final diagram on the right that some of that water has been left in the container.

If we had poured any further, some of the sand would have left the container with the water.

So I haven't managed to fully separate it, so I'm gonna have to think of something else.

Another option I might use to separate those insoluble substances from a mixture is filtration.

And I might use filtration because it's far better at fully separating those insoluble substances from a mixture, but it does need some specific equipment.

The first and foremost that it needs is filter paper, because this is where the mixture is actually going to be separated.

The thing is filter paper can be quite flimsy, so you tend to need a funnel, because what that does is support the filter paper in its role of separating that mixture.

And then finally you're going to need a container.

It's usually a conical flask that is used, but that container then is able to support the funnel and collect the liquid and any soluble components that were in your mixture.

So it's a two for one job with that container.

Let's stop here for a quick check.

Why is filtration a better technique for separating an insoluble component in a liquid than using decanting? You may wish to pause the video to read through your options, and chat over the ideas with the people nearest you, and then come back when you're ready to check your answer.

Well done if you chose C.

Filtering can fully separate an insoluble component from a mixture.

A won't work because filtering requires one of those components to be an insoluble substance.

And two, liquid materials would be able to travel through the filter paper.

The filtering doesn't necessarily be a faster technique depending on the particle sizes that are being separated.

And we'll learn more about that later on in the lesson.

But well done if you managed to choose C.

Good job, guys, a great start.

Now I said earlier that one of the key pieces of equipment that's needed for filtration is that filter paper.

And that's because that is actually where the mixture is being separated.

So we need to make sure that it's prepared properly.

A lot of times, I see people just randomly trying to squish it into the filter paper or, horror of all horrors, using scissors, cutting a slit in it so that it more easily can be folded to fit into the funnel.

But there is a better way of doing this, and that is simply folding it.

So you'll take your filter paper, you fold it in half, and then fold it in half again.

So you end up with something that looks a little bit like a a wafer that you might use in an ice cream cone, okay? It's folded into quarters.

At this point then, your filter paper will, if you look at it on the rounded edge, it should have four different layers of paper to it.

If you put your finger between those layers, you should have one layer on one side and three on the other.

And what that does then is it opens up one of the quarters and it turns that folded paper into a pocket, which will very easily fit into the funnel that's supporting it.

Now if for some reason it pops back out of that funnel, all you need to do is hold it in place with two fingers and then simply add a drop of water to the centre of that filter paper, and that will help keep it against the funnel so that you can continue.

And it's simple as that, but it's a very important part of preparing to do filtration.

Now once you have properly prepared your filter paper, place it in your funnel.

Then you are going to gently swirl the mixture you're trying to separate and then gradually pour it into that filter paper.

And it's very important obviously that that funnel and filter paper are being supported by the container.

So this is why we tend to use a container that has a narrow neck, because the funnel tends to have quite a narrow opening at the bottom, and therefore you need a narrow neck container.

Conical flasks are used most frequently.

Beaker is not because they have a far wider neck.

You can see here in the picture what's being poured out of is that beaker.

And what that does then is it makes the funnel flip to the side, and so the filtration is less efficient, and it's more likely that what you're trying to separate will actually go over the top of the filter paper, and actually you're not separating anymore, it's just getting all messed up.

You could use as well a boiling tube or a test tube depending on the volume of the mixture that you're trying to separate, but a conical flask tends to be the best because it also prevents spillage.

So we folded our filter paper, supported it properly in our funnel.

We've set it up with an appropriately narrow-necked container.

We've poured our mixture gradually through that filter paper.

And what we now have at the end of filtration are two main components from our starting mixture.

What we have, first of all, is the residue.

That is the insoluble solids that have been removed from your mixture.

So if you were then able to pull out and open up that filter paper that had been folded in the funnel, you'll see then this residue that's collected on it.

The next thing you'll have then is the filtrate.

That's the liquid, what was able to pass through our filter paper.

And that will include not only the the liquid of our mixture but also any soluble substances that were in it as well.

So two main parts, the residue, which is insoluble and collects in the filter paper, and then the filtrate, which is the leftover bits, the liquid, and any soluble substances in the filtrate.

And that collects in the container.

Time for another quick check.

Which two of these statements are correct? Now they're a little bit long.

You might wanna discuss the wording of them a little bit.

So I would recommend pausing the video here and coming back when you're ready to check your answer.

Okay, let's see how you got on.

Well done if you managed to choose B and C.

So the correct statements were the residue is the insoluble solid collected in the filter paper and the filtrate is the liquid that's collected in the flask that may contain dissolved substances.

A is incorrect because the residue should be non-dissolved or insoluble substances.

And it is collected in the filter paper, not the conical flask.

So that's why A was incorrect.

D was incorrect because it says the filtrate is the insoluble solid.

And actually the filtrate should be the liquid and any soluble solids.

And that is going to be collected in the container, not the filter paper.

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

And give yourself a pat on the back as well if you've got at least one of those correct.

Good job, guys.

Okay, time for the first task of today's lesson.

We have here a setup to carry out filtration.

And what I'd like you to do is to label the equipment and also describe the use of that.

What is its function? What is its job as part of this filtration setup? To get you started, I've given you one use and I have labelled one piece of equipment, just to give you an idea.

What I would recommend here as well is that you're writing this in pencil, so if you want to change anything later when we go through the answers, it's easier for you to do so.

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

Okay, let's see how you got on.

So the very first piece of equipment you were actually given the use for, it's where the filter paper sits and what supports that filter paper.

And that is the funnel.

What is the next piece of equipment is what's sitting in that funnel, and there was a hint in the previous use.

It's the filter paper.

So the filter paper is what actually separates that insoluble solid and liquid in the mixture.

It's where filtration and separation takes place.

It might have been a little tricky for you to see the next label, but it's actually pointing at that darker section within the filter paper, and that is the residue.

Now the residue is simply the insoluble component that is collected in that filter paper.

It's what's been separated out of that particular mixture.

I've told you that the name of the equipment, the next, is the conical flask.

But its job and its role within filtration is simply to support that filter and the funnel.

And it's where then as well where the liquid is going to be collected.

And then finally, that liquid is actually referred to as the filtrate because it's what's collected as a result of filtration.

And the filtrate then is not only the liquid, but it also contains any soluble substances that might be collected from that filtered mixture.

So great job, guys.

Well done if you managed to at least label the different pieces of equipment.

And very, very well done if you managed to also include the use or description of those key terms particularly for residue and filtrate.

What a fantastic start to the lesson, guys.

Really impressed.

So now that we're feeling a little bit more comfortable with the setup that might be used for filtration and what kinds of mixtures filtration might be most useful for, let's move on to discuss what's actually happening.

How can we explain what's going on during filtration? Sometimes it helps that when you are trying to explain a technique or different ideas in science to have an understanding of the uses in the back of your head just to jog your memory about what's actually going on here.

So the thing to remember is that filtration is actually a very, very common separation technique.

A really good example is a mask.

We'll be very familiar with these.

Now masks separate the fine particles that are found in air, to make sure that what you're breathing is a little bit cleaner, so you're not getting some of those dust particles, for instance, in your lungs.

The other thing you might find it used for is air filters in a car.

This is regularly checked, if anybody has an MOT that's done in their cars, which is necessary for people to tax their cars and be able to drive them on the road.

So air filters are found in every car.

And that helps to prevent any contaminants from entering the engine.

So again, it's doing the job of preventing different fine particles from making their way in to a device that might prevent it from doing its job properly.

But more commonly, we might actually see that filters are being used when making coffee or tea.

And what that does is it's removing those solid particles that were used to make the drink in the first place.

So as we go through and try and explain filtration, it might help to have any of these really common uses of filtration in the back of your head to help just remind you of what's going on.

The main thing to remember about filtration is that for it to be successful, you need to have the right filter.

Now we talked previously about filter paper, but that's not the only type of filter that can be used.

Some filters actually have holes that are simply small enough to allow any liquid and any of those dissolved substances to go through them, but it stops those larger particles from being able to get through.

So if we think of almost like a sieve, here looking a little bit like netting.

That is effectively a filter with holes.

Now that's gonna be able to stop large, insoluble, solid particles from going through, and then the liquid and any dissolved substances are able to pass through it.

A really good example of this are any colanders that you might use.

That would be your filter with the holes.

Your insoluble solid then in this example is strawberries, but it could be any vegetables that you might use or pasta that you're trying to drain.

And then the filtrate, or the liquid with those dissolved substances passing through it, are able to because of the size of those holes.

They're able to pass through, whilst those strawberries, pasta, whatever are left within your filter.

Now the same idea holds true when you're talking about other filters, things like filter paper, air filters, masks, things like that.

They have what are known as tiny pores that act as the holes, that are small enough for those liquids and dissolved substances to pass through.

But those larger particles are stopped.

So if we look at our filter paper, you can't see any holes.

We can't see any pores in there.

So it doesn't make sense that it can act as a filter.

But if you were to look at it a little bit more closely, we can see that there are paper particles, but between those paper particles, there are pores, those little gaps between those paper particles.

And that's where our fluid is able to pass through it.

Now I'm talking about fluids mostly about liquids, but this type of thing also works specifically when we're looking at masks.

It acts like the filter paper.

So the substances is being separated.

And our mixture, we can see here we've got some red and some grey gases that are going towards it.

But that filter paper, with those really tiny pores, are able to just let one of those gases through.

And the other larger particles are stopped because they're not small enough to fit through the pores of our filter paper.

Let's stop here now for another quick check.

How would you describe the size of the pores in the filter paper compared to the size of the residue particles? Well done if you said B.

The pores need to be smaller so that the residue particles are stopped from passing through.

If they're the same size or larger than those residue particles, the residue, or what's meant to be the insoluble solid that's separated, will still be able to pass through and filtration won't take place.

So they must be smaller than the residue particles.

Well done if you managed to get that correct.

Let's try another one.

True or false, dissolved coffee particles are larger than the holes in the filter? Well done if you said false.

But which of these statements best supports that answer? Well done if you said A.

Dissolved particles should be able to pass through the filter.

And for that to happen, those particles actually need to be smaller than the holes in the filter, not larger than the holes in the filter.

Dissolved particles would actually pass through, and therefore they would not remain in the filter.

Insoluble or undissolved particles would remain in the filter.

So well done if you managed to get that correctly justified answer of dissolved particles can pass through the filter.

Good job, guys.

Now the thing that I've also seen when people are performing filtration is they get really frustrated, because the pores of the filter paper, especially when you're using incredibly fine, insoluble substances, things like chalk, that need to be removed, that means that they can really easily block the filter paper.

So we can see here, we've got our zoomed in view of the filter paper, we've got our open pores, the spaces between those paper particles, and then the blocked pore.

And what tends to happen is people try to use a pencil or a stirring rod and try and push it through.

And really, what you're gonna end up doing is actually ripping that filter paper and making those pores even bigger, which would stop it from doing its job.

It wouldn't be able to stop those insoluble substances anymore, and you'd have to start again.

So a way to try and stop this is we know that this blocked filter paper is gonna slow this filtration.

So sometimes filtration is an exercise in patience.

You just need to let it do its job.

Because if you do try and pour too much and that filter paper is blocked, it could possibly overflow the filter paper and go through the funnel and into your filtrate.

One way to prevent this is to pour slowly, okay? Only pour a little bit at a time and make sure that you swirl your mixture before you pour it, gradually do it.

And that will help to prevent those pores from becoming blocked, particularly towards the pointed part of your filter paper, which is where it has the greatest access to the spout of your funnel.

Let's have a go at another quick check now.

True or false, a mixture should be swirled and gradually poured into the filter paper? Well done if you said true.

But which of these statements best justifies that choice? Well done if you said B.

Swirling and gradually pouring your mixture into the filter paper is gonna help to prevent that filter paper from blocking.

What it won't do is help the residue to pass through the filter.

We don't want that.

We want the residue to stay in the filter, okay? So very well done if you managed to get that correct.

Guys, you're doing a cracking job today.

Okay, guys, let's move on to the next task in today's lesson.

So Jacob here knows that there are loads of sources of salt in the world, many different places where we can get the salt from that we use.

But most of those sources are impure sources of salt.

So I'd like you to help Jacob find out how to remove the insoluble impurities that come with a source of salt.

So the first thing I'd like you to do, please, is to match Jacob's ideas to the equipment he's been given.

So take a moment here, pause the video, and come back when you're ready to check your answer.

Okay, let's see how you got on.

So if I'm going to crush the sample of dirty rock salt, I'm going to need to use the equipment in the centre, which is known as a mortar and pestle.

If I'm going to filter the solution, I'm going to be using the equipment on the far right, which shows us with our filter paper, funnel, and conical flask.

And I'm going to need to add water to dissolve the salt from that sample in the first place.

If I've just got a source of salt, that's gonna be a solid on its own.

In order to separate it using filtration, I need to add water first.

So very, very well done if you managed to match up those ideas to the correct pieces of equipment needed.

Good job, guys.

Now that you've matched up the ideas and the equipment, I'd like you to please put each pair, that's the picture and description, into a logical order to help Jacob remove those insoluble impurities from the salt.

So in what order would you use this equipment? Pause the video and come back when you're ready to check your answer.

Okay, let's see how you got on.

So the first thing Jacob needs to do to separate the insoluble impurity from the salt is he needs to crush that sample of dirty rock salt.

What that's gonna do is open up any large pieces so that he's able to dissolve more of the salt and remove more of those insoluble pieces.

Now, I said dissolve.

That means the next thing he needs to do is add water in order to dissolve that salt from the sample.

Once he's managed to do that, he's got as much salt into the water, and then he's gonna be able to simply swirl and gradually pour that solution into his filtration setup in order to separate out those insoluble impurities.

So the correct order was B, C, and then A.

So well done if you managed to get that correct, guys.

Great job.

Okay, for this last part of today's lesson, what I'd like you to do is follow the method that you created in task B, 1-B, and I'd like you to try to remove then some insoluble impurities from impure salt.

If you're at home, you might have rock salt at hand.

I know that rock salt is used to remove ice and snow from outside.

You might have some in the garage.

If not, there is a video here that'll show you a demonstration of how it can be done.

Now we said that sometimes filtration is an exercise in patience.

So while that is filtering, what you could do is try to explain why filtration works for separating impure salt from the impurities that it might have.

And then what I'd like you to try to do is include some of these keywords that we've been looking at today, so the words soluble, insoluble, residue, and filtrate in your answer.

So as you're working through that, I would challenge you to highlight, or underline, put a box around each of these keywords as you use them so that you can see how they're being used.

And then think about why might this salt that you are filtering out still not be usable? So follow the method to create your, to separate out, sorry, your insoluble impurities from impure salt.

Write a little paragraph to tell me how filtration works for this separation.

And then finally, think about how that salt might not be usable still.

This might take some time, so pause the video here then and come back when you're ready to check your answers.

So what we have here then is the rock salt sample.

And we're gonna take a bit of that and put it into the mortar and pestle.

And then you're gonna grind this with a pressure and a circular kind of twisting motion in order to break up as much as we can.

Pour it into a beaker, and then add some water, and stir to dissolve.

We prepare our filter paper then by folding it into quarters, opening up that pocket, and then placing it into the funnel.

Add a few drops of water to keep it in place, and then slowly and gradually pour our mixture into our funnel.

And we can see that the filtrate is coming down the bottom.

And we can see the residue, look how dirty that is, start to collect into our filter paper at the top.

Okay, let's see how you got on.

Now, if you were able to follow that method to be able to remove impure, insoluble substances from that salt sample, then you will have collected your filtrate, which should look colourless and clear, so there's no bits in it, and you could see straight through it, and that will be your salty water.

And then you'd be able to discard the residue, any darker, impure, insoluble substances that was collected in your filter paper.

So very well done if you managed to do that.

The second thing I asked you to do is to explain why using filtration works to separate out those insoluble impurities from the salt sample.

So what I've done is I haven't underline or highlighted, what I have is bolded the keywords as I used them so that we can double check that I've tried to use all of those keywords and have used them appropriately.

So your answer might be something along these lines.

I've said, when water is added to the impure salt, the soluble salt dissolves, while the insoluble impurities do not.

If the mixture is then poured through filter paper, the insoluble impurities collect as residue as the particles are too large to pass through the pores in the filter paper.

The salt remains in the filtrate.

Now your answer won't match this completely, but what you can see here is I have bolded those keywords so I can see where they've been used.

And what I really like about this is that I've had soluble salt.

So that immediately makes me think of salt being soluble.

Insoluble impurities, they're being removed.

So the other words nearby, these bolded words that I've created in my paragraph here, make it easier for me to make links if I was to have to read through it really quickly later on, which is why I've suggested highlighting, underlining, or circling them in your own answers.

Now for the last question, I asked you to think about why this salt might still not be usable.

And what you need to do is remember that the salt is still dissolved in the water.

It's still in the filtrate.

I don't put salt water on my soup, okay? I don't put salt water.

I shake it out of a salt shaker.

So it's still not usable in its current form.

So I'm gonna have to think about another way that I'm gonna be able to get this salt out of the now mixture of salt and water.

Really, a fantastic job, guys, today so far on these tasks.

You've been doing just a fantastically cracking job.

So great job, guys.

So we've gone through quite a lot today, but let's just summarise what we've managed to learn.

Well, we've learned that filtration is a technique that's used specifically to separate insoluble substances from a liquid in a mixture.

We've also learned these terms. A filtrate and residue can be used to describe the components that are separated by the process of filtration.

And we remember that the residue is that insoluble solid that collects in the filter paper.

And the filtrate then is the liquid and any dissolved or soluble substances that's collected in our container.

We've also learned that separation using filtration occurs purely because of a difference in size, particle size, between the residue and filtrate particles.

And that can be controlled by the type of filter that you use.

There's lots of different filters out there.

I hope you guys had a great time learning with me today.

I've had a great time with you.

And I hope to see you again soon.

Bye for now.