Hello, my name's Mrs. Niven, and today we're gonna be looking at how we can separate an insoluble solid from a liquid as we start our journey through this topic of separation techniques.

You may have some experience of these processes in some of your previous learning, but it is a mighty important topic as we move forward in our journey through science, particularly as we start to consider how we might be able to separate out what is made in chemical reactions as we go forward.

By the end of today's lesson, you should be able to use your understanding of the properties of some solids and liquids in order to work out the best way in which to separate out the parts of some mixtures.

The keywords that we're gonna be using throughout today's lesson are filtration, filter paper, filter funnel, residue, and filtrate.

Now, the definitions for these keywords are given on the next slide in sentence form and you may wish to pause the video here so you can read through them or perhaps make a quick note of them for you to refer to throughout the lesson.

Today's lesson has three main parts.

First, we'll look at the properties of insoluble solids, then we'll move on to see how we can use those properties to decide the best method, which to separate them from liquids.

And finally, we'll look more in depth the process of filtering mixtures.

So let's get started by looking at the properties of insoluble solids.

There are many materials in the world that simply won't dissolve in water, and some examples are iron, wool and sand.

And materials that will not dissolve in a particular solvent are known as insoluble substances.

So that means if you were to put that substance into water, you'd still be able to see it.

Now, the thing about insoluble solids and liquids is that you can still put them together, but they'll form a mixture.

And crucially, a mixture can be physically separated, which means we need to look at the physical properties of these materials to decide what's the best way in which to separate them.

So by definition, insoluble solids will not dissolve in a liquid, and we can actually use the properties of those insoluble solids to decide the best way to separate them from that liquid.

For instance, some insoluble solids are more dense than the liquid in which they've been put, and therefore will sink to the bottom of the liquid or the bottom of that container.

Other insoluble solids might actually be less dense than the liquid in which they're put and therefore start to float at the top.

Now, this is one property, but because they are two different insoluble solids, one will sink and one will float, and we can exploit these properties, this one property of density, to decide what is the best way to separate these two different insoluble solids.

Another physical property that insoluble solids might have besides their density is the size of their particles.

You have here an example of six different insoluble solids, but some of these particles, for instance, the pebbles and the pepper, are far larger than, for instance, the flour, the soil, or the iron filings.

So the size of these particles might also impact the best method that we might use in order to separate out these insoluble solids from our liquids.

Let's pause for a moment for a quick check to see how you're getting on.

Which substance listed here do you think would completely sink to the bottom of a container? And I'd like you to justify your answer.

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

Well done if you chose C, pebbles.

But how did you come to that decision? Why is it pebbles? You could have said pebbles have larger particles and are more dense than water.

And I know that because I've seen pebbles in a river at the bottom of the river, not floating along at the top, usually.

Now, soil and flour contain finer particles and so are more likely to float in water.

And again, I've seen that, the flour, when I put it into a mixing bowl, tends to stay to the top, and the same thing with soil, I might see that floating at the top of a river as well.

So using what I've experienced outside of the classroom has helped me to answer this question a little bit better.

Well done for a tricky task.

Now, if you've ever gone walking around a waterway like a canal, a river or a stream, sadly, sometimes you might have come across some litter.

I've seen it for instance, of fizzy drinks cans, of crisp wrappers, of other little metal containers, even bicycles and shopping trolleys, sadly.

And a lot of times people will be picking up or removing these by hand, but sometimes people think that you could possibly use a magnet to collect any pieces that have maybe ripped apart.

And the problem with that is that most metals are not actually magnetic.

The only magnetic materials or metals that we have are iron, nickel, cobalt, and steel.

But those particular magnetic materials could actually be separated or removed from a mixture including the environment, using a magnet.

Now, we've got to be careful using magnets, okay? Because they can be quite powerful even if they're quite small.

But it is one method that could be used to remove one of our insoluble solids.

If it's a metal and it's a magnetic material, you could use a magnet to remove it.

Let's have another quick check.

I'd like you to consider this question.

Which of the following metallic items could be separated from a liquid using a magnet? And it's okay to just have a think here.

There's no right or wrong answer.

But what I'd like you to consider then is two everyday objects.

You've got your steel paper clips that you might use to attach some papers together, and then you have some copper coins.

So I'm thinking of one P and two P pennies.

So have a think.

And then I'd also like you to justify why you've put your tick in the specific box you've chosen.

So why do you think this is right? Why do you think it might be right, might be wrong, or you're definitely sure that it's wrong? Pause the video here and come back when you're ready to check your answers.

Okay, let's see how you got on.

Now, for any who said the steel paper clips, I am pretty sure that this is right, and for copper coins, pretty sure that this is wrong.

And that's because if you remember, steel is a magnetic material.

It's one of our four.

And the way I remember it is a really silly acronym called SINC, S-I-N-C, for steel, iron, nickel, and cobalt.

Those are the only four of our metallic materials that you can be using a magnet with.

Copper is not the C, it's cobalt.

So it's quite a tricky one to remember, but it's non-magnetic.

And because of that you cannot use a magnet to remove it.

Okay, time for our first task.

So Aisha and Izzy are deciding which properties of the iron filings the pebbles and the seeds are important when separating them from a mixture.

So all three of these materials are in the same mixture.

And what I'd like you to do is I'd like you to suggest a method to fully separate out the mixture that contains all three of these.

This may take a little bit of time.

You might want to discuss this with the people nearest you to jot down your ideas.

But take a moment, pause the video and come back when you're ready to check your answers.

Okay, let's see how you got on.

Now, there were a variety of ways in which you could have done this.

There's no specific order in which to do this, but your answer may have included the use of any one of these four steps.

So one thing you could have done is added water to the mixture, actually putting water into it and creating a fourth substance in this mixture.

And there's a reason for that.

By adding water, the seeds would be quite less dense and therefore would float to the very top.

And by doing that, you could simply pull them out by hand.

Okay? The other thing you could do then is notice that we had iron filings in there? That was the eye out of our SINC, S-I-N-C.

So that means it is a magnetic material and therefore I could use a magnet to remove those iron filings from the pebbles.

And then the pebbles, because they're so heavy, would sink to the bottom of my substance.

And then all I'd need to do is figure out how to get rid of the water or I could, again, stick my hand in and try and pull them out, but that's probably gonna make a bit of a mess, but it could be done.

So lots of different ways you could have used to, but we say there were multiple different processes and are very useful just adding that water and using the magnet.

That's probably the two main things I would've looked for.

Did you add water so the seeds could be removed easily, and did you use a magnet? Because the iron filings tend to be quite tiny and we don't want to miss any.

Using a magnet would mean we didn't miss any.

Quite a tricky task there.

Well done for having a go.

Now that we're feeling a little bit more comfortable talking about the properties of insoluble solids, let's look at some of the different techniques we might be able to use to separate them from a liquid.

Now, I mentioned earlier that one of the physical properties of insoluble solids that might impact the method we use to separate it from a liquid was the size of the particles.

So let's look at an example now.

In here, I have marbles that have been put into some water.

So I do have a mixture here because it's two different materials that could be separated physically.

Now, the marbles here are large and I could literally just pop my hand in and pick them out one by one.

Another insoluble solid is sand, but those particles are very small.

So I'm gonna need to use a different method to separate it entirely from the liquid because if I went in with my hand to try and pick them out one by one, I'd be there for a very long time, and also I might miss a few and I really don't want to miss a few.

Now, despite the sand particles being very small, they are quite dense, more dense than water, in fact.

And because of that, they'll fall to the bottom of the container.

And one of the things I could do to separate out the sand from the water is simply to pour the water off because the sand has fallen to the bottom of that container.

So if I pour it out a little bit like this, this is known as decanting.

So when I decant out something, what I'm essentially doing is pouring one layer of my mixture out.

There is a slight problem with using this process though.

Can you find it using the pictures? Have you found it? The problem with using decanting is that some of that layer that you have tried to pour out in this instance, the water, has remained, so I haven't completely separated my sand from the water.

Some of the water is still there because if I pour it any further, some of that sand might also pour out with the water.

And again, I don't want to lose any.

Let's pause here for a quick check to see how you're getting on.

True or false, soil is insoluble in water and can be separated from water by using your hands to pick up the particles? Well done if you said false.

But what's the reason for that? Is it that the soil particles will dissolve in the water or is it that the soil particles are too small to be individually picked out? Well done if you chose B.

Those soil particles are insoluble, as it said in the statement at the top, and they are simply too small to be individually picked out of the liquid.

Like our sand, some of it might get lost along the way.

So you may have noticed a growing trend here that small insoluble particles are very difficult to separate out by hand or bind decanting fully to make sure that we have completely separated out our insoluble solid from the liquid.

So we need a different method in order to do that.

And a better method to use is something called filtering or filtration.

Now, during filtration, what happens is that insoluble solid is separated from the liquid by passing the entire mixture through a filter.

So an example here is actually used in everyday life.

So if you've ever seen somebody make a cup of coffee, I'm quite the fan myself, that hot water is passed over some ground coffee beans, and then anything that's insoluble will stay in the filter paper and not go into my coffee, which is quite good.

Nobody likes the little grainy bits in their drinks.

Another example you might be a little more familiar with is if you're ever straining off the water from say rice that's been cooked, or if you've made some pasta and you've used a colander, that's another example of filtration where you catch your insoluble substance, the pasta, and anything that's soluble or liquid, for instance, the water or some of the starch that's come out, will go through the holes in your filter.

Let's pause for another quick check.

Why is filtration a better separation technique for separating an insoluble solid and a liquid than using a magnet or decanting? Pause the video here and come back when you're ready to check your answer.

Well done if you chose C, filtering separates an insoluble solid and a liquid mixture.

A is incorrect because it's not filtering that separates magnetic and non-magnetic materials.

You need a magnet for that to work.

And B, filtering takes less time.

Well, I don't know, not always.

We know that possibly filtering out pasta from water is quite quick, but is making coffee quite quick? Making a cup of tea where our filter of our teabag acts as the filter? Maybe not so much.

So let's take a closer look.

So regardless of the type of filter you're using, so if you're using a strainer, a colander, a teabag or a filter for a coffee machine, they're all working in the same way.

They are stopping an insoluble solid from passing through it.

And it does that because it has some small holes in it that allow that liquid with the dissolved substances to pass through it.

And what it does then is stop those larger, insoluble solids from passing through.

So we can see here that the diagram shows our filter with the holes and the insoluble solid that has been caught and not allowed through those holes because they're too large and then the liquid that contains those dissolved substances are able to pass through it.

Now, you might be sat there wondering, how is it possible that a strainer or a colander can have anything in common with a teabag or a coffee filter? And the point is that it doesn't matter what type of filter you're using, they work in a similar way.

They are some form of grid structure that is going to stop an insoluble solid from going through and allow your liquid and dissolved substances through in some way.

Now, if we look at a filter paper, it doesn't have holes so that you can see, but if we look at it a lot closer, it has tiny pores and it's those tiny pores that are small enough to let that liquid and dissolved substance through.

So for instance here, if we look at the filter paper, you cannot see the holes in it, but if you were to zoom in, you can see that we have the paper particles acting as the solid structure of our filter paper, but that space between those paper particles act as pores and that's where that liquid and dissolved substances are able to pass through, but the small insoluble solid particles are not.

Time for another quick check.

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

But what's the reason why? Pause the video here and come back when you're ready to check your answer.

Well done if you said A, dissolved particles are smaller than the holes in the filter because they can pass through.

If you remember this whole time, the filter is going to stop insoluble substances from passing through, but the holes or the pores will allow the liquid and the dissolved substances, so the particles that have dissolved, through that filter paper.

Well done on a tricky task.

Time to move on to our second task of today's lesson.

We've now talked about a few different methods that could be used to separate an insoluble solid from a liquid.

So what I'd like you to do is to complete this table to tell me which method do you think would be best to separate each of these insoluble substances from a container of water.

So they're all in their own separate container of water.

You could consider six different cups of water, one with the flour and water, one with rice and water, one with iron filings and water, all the way through.

So the first thing I'd like you to do is to decide which method do you think would be best to separate them from the water.

And if you finish that, I'd like you to justify your choices for me.

This might take a little bit of time, so please pause the video here and come back when you're ready to check your answers.

Let's see how you got on.

Now, if you completed your table correctly, it should look a little bit like this.

The magnet's only going to be able to separate out any magnetic materials, but iron is one of our four magnetic metals and therefore, the magnet would be able to remove the iron filings.

Decanting works when you have some substances that are heavy and will fall to the bottom of the container.

So definitely the pebbles, the rice wood as well.

Filtering is gonna be needed for any materials that have very small particles.

So that's gonna include the flour, the pepper, and the soil.

So if you were to justify your answers using separate sentences, some of your sentences may be including these.

That iron is the only magnetic material here, therefore it's a magnet that's gonna work.

The pebbles and rice are large and dense, and so those sink to the bottom of our liquids, so decanting works.

Then for the flour, pepper and soil, we needed to say something about the fact that they are smaller or less dense materials, and so they're not gonna dissolve, but they're gonna be harder to remove than if we just use decanting alone.

And that's to remove fully, to fully separate out the insoluble substance and all of the liquid.

Now, another option is that we could have said is that filtering could have also been used to separate out the pebbles and rice, but really, when we're talking about choosing which method to separate out a mixture, we want to look at what's gonna be the easiest.

Am I gonna need extra equipment or extra materials in order to do this? Decanting, I just need to pour it out.

So if it's a quick and easy way of doing it, I'm gonna try that one first.

Well done, particularly for justifying your choices on here.

Now that we are feeling far more comfortable talking about the different properties that might be used to separate out an insoluble solid from a liquid and looking at the methods we might use depending on those properties, let's take a closer look at what's happening in filtering.

Now, I mentioned that filtering or filtration is used in everyday life in loads of different situations, usually in the kitchen, but in a science laboratory we use specific equipment for filtration, and that is this.

The first thing we're gonna need is a filter funnel, and that's where the filter paper is going to sit and be supported by.

The filter paper then is where the mixture actually pours.

So this is where that insoluble solid is going to be collected and the liquid is able to pass through the pores within that filter paper.

It's where the separation actually takes place.

The residue then is going to be what we call any insoluble solid that is collected or stopped by that filter paper.

Now, the filter funnel you can see is actually supported and placed in a conical flask.

Now, the conical flask there is collecting the liquid and those soluble substances that have passed through the pores of the filter paper.

And we refer to any of that mixture, the liquid and any soluble substances that go through it, called the filtrate.

So that's the liquid and soluble substances that have passed through that filter paper.

If you have a pen and paper handy, it might be worth pausing the video here to jot down this diagram and all the labels with definitions because it's quite a handy diagram to refer back to whenever you're going forward talking about separation techniques.

Now, the most important part of our filtration setup is how the filter paper is prepared so that it can sit in the funnel correctly and do it's job of collecting that insoluble solid or residue.

So the first thing you're going to do is take your filter paper that sits as a very thin piece of circular paper and fold it in half once and then a second time.

So you're taking your full piece of paper and making it look like a quarter.

Now, when that happens, what you have then, if you look at it from the curved end straight down, is four different pieces of paper.

What you're going to do is you're going to put your finger between one on one side and three pieces of paper on the other.

And what that does then is it opens up the quarters to make a pocket.

So there's no unfolding of this filter paper, there's no strips of the funnel that you can see when you put it into that funnel.

You're going to have this pocket that looks a little bit like an ice cream cone and you're going to put the pointed end into the V-shaped part of your filter funnel.

Now, sometimes when you do this, that paper will pop back out in the funnel and we don't want that to happen.

So one way to keep that filter paper positioned in the funnel correctly is to just add a drop of water at the pointed end of the filter paper, and that will help kind of stick it to the funnel and help keep it in place.

So now that you have your filtration set up properly prepared with your filter paper properly folded and placed into the filter funnel, you are ready to actually pour your mixture into that filter paper.

Now, before you do that, what you want to do is to take your mixture and swirl it a little bit before you pour it into that filter paper.

And what that does is it helps to prevent the pores within the filter paper from clogging.

Sometimes if those pores become clogged, it slows down the filtration process.

And I would challenge you here to have patience.

Okay? Filtration's gonna be slow.

Remember, those pores are really tiny and there is sometimes a temptation to push through the solid materials or try to move them out of the way.

And what that does is actually possibly rip that filter paper.

And if that happens, you're gonna have to start all over again.

So do not be tempted to poke anything into the filter paper once you've started pouring your mixture into it.

Okay? The other thing you want to make sure is to not pour this liquid continuously.

What you can do is pour a little bit in only until it reaches just below that filter paper because if it goes over the filter paper, even though the funnel is big enough to hold the liquid substance, if you pour that in, the liquid could then push up and over the filter paper, behind it, and then some of those particles, especially those lighter weight, smaller ones, can go in that space between the funnel and your filter paper.

So it's really important you're pouring slowly, and that you're not overflowing it.

The other thing that you want to make sure of is when you are putting your funnel into the conical flask that it's nice and secure.

One of the reasons that we use a funnel with a conical flask rather than something like a beaker is that because it has that narrow neck, the funnel is supported really, really well on the angled bits of it, in the kind of V-shaped part of that funnel.

So always make sure you're using this with a narrow neck piece of glassware.

So now that you were able to pour your mixture involving an insoluble solid and a liquid through your properly prepared filtration setup, what have you got? Well, essentially, you should be able to see the insoluble substances having been stopped by that filter paper.

And if you are able to remove it very carefully so it doesn't rip and then unfold it, then in the centre of that filter, open filter paper, you would see that residue, that insoluble solid that has been collected.

And then left in the conical flask below would be the filtrate.

That's the liquid and any soluble substances that were able to pass through the pores of that filter paper.

Okay, let's try a few more quick checks to see how you're getting on.

True or false, the mixture should be swirled and gradually poured into the filter paper? Well done if you said true, but what's the reason for this? Pause the video so you could read through these properly, have a discussion and then come back when you're ready to check your answer.

Well done if you said B.

This helps to prevent the filter paper from blocking, which would cause the filter funnel to overflow.

Well done on that task.

Let's try another one.

Which two of these statements are correct? You'll want to pause the video here to read through them and come back when you're ready to check your answers.

Well done if you chose B and C.

A is an incorrect statement because the residue should be the undissolved or insoluble substances in the liquid, and that's gonna be collected in the filter paper, not the conical flask.

D is an incorrect statement because the filtrate has the soluble solids in the liquid and that's gonna be collected in the conical flask.

So there were two different clues in each of those sentences to say that they were incorrect statements, but well done if you managed to choose at least one of the correct statements.

Good job.

One more check.

How would you describe the size of the pores in the filter paper compared to the size of the residue particles? This is a tricky one, so you might want to pause the video so you can discuss the options with the people nearest to you and come back to check your answer when you're ready.

Well done if you chose B.

The size of the pores in the filter paper must be smaller than the residue particles.

If it was the same size as the residue particle or even larger than it, then those particles would be able to pass through and you wouldn't be able to stop them.

So the pores must be smaller so that the residue particles are stopped from going through and therefore collected in the filter paper.

That was definitely a tricky, tricky question.

Well done if you managed to get it correct.

Time for the last task in today's lesson.

What I'd like you to do is to use the diagram on the left to label each of the equipment that's been shown here, but also to fill in the use for that particular piece of equipment.

Why is it needed or what is it's purpose within this process of filtering mixtures or filtration? Pause the video here because it will take a little bit of time and then come back when you're ready to check your answers.

Okay, let's see how you got on.

Well, that very first piece of equipment labelled at the top is known as the filter funnel.

And if you couldn't tell from it's diagram, you could also have figured it out from the use because it's where the filter paper's gonna sit and where it is being supported.

Now, the next bit that has shown, the label here, is the filter paper.

And the filter paper is the most important part of this entire setup because that is the piece of equipment that is separating out that insoluble solid from the liquid in the mixture.

Now, the next line down is pointing to a brownish or darker colour within our filter paper, and that indicates the residue, and we know that as well because it's at the most pointed part or the most bottommost part of the filter paper as it's shown in our diagram here, but the residue is essentially the insoluble solid that's been collected in that filter paper.

Next, I've given you the name of a conical flask, but what is it's purpose or job or use in this particular setup? And really, what it's doing is it's both supporting that filter funnel, keeping it upright because of the narrow neck of a conical flask, but it's also where the liquid and any soluble substances that are able to pass through the pores of our filter paper are collected.

And finally then we have our filtrate, what's actually dripping into our conical flask.

And as said before, it's the liquid and any soluble substances that are going through that filter paper are going to be collected here.

So we're able to collect the residue in the filter paper and the filtrate is collected in the conical flask.

Well done if you managed to firstly name each piece of equipment, but even better if you managed to also describe their use.

Good job, guys.

Okay, let's summarise what we've managed to do in today's lesson about separating an insoluble solid from a liquid.

Well, we've learned a variety of things, including that magnets can be used to separate out any magnetic materials from a mixture, and those magnetic materials are steel, iron, nickel, and cobalt, SINC.

We've also learned that a filter can be used to separate out insoluble solids from liquids and that a lot of these can be found in everyday use.

Things like colanders, strainers, filter papers, things like that.

But in the lab, filtration itself involves taking a mixture and gradually pouring it through a folded piece of filter paper that's been opened up in a filter funnel and that it's sitting in a conical flask.

So we're using very specific pieces of equipment in order to carry out filtration within the laboratory.

And then when that has finished separating out, the insoluble solid that's collected in the filter paper is called the residue, and the liquid with any soluble substances is collected in the conical flask, and that is called the filtrate.

I hope you've had a good time learning with me today and to see you again here soon.