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Hello, everybody.

Hello from me, and from Charlie.

Oh, he's off outside.

It's too sunny for him.

Today, we are doing our next lesson in our unit, and I'm really excited to get started.

So, let's begin.

Our lesson question today is how can mixtures be separated? We've learned before that a mixture is a substance with more than one type of particle.

So if I were to add sugar to my water, it would be a mixture, because it's got sugar particles and water particles in it.

Today, we're going to learn how to separate mixtures.

For this lesson, you will need a piece of paper, a pencil, a colouring pencil, and a ruler.

If you don't have those things, pause the video and go and grab them for me now, please, These are our star words for this lesson.

So I'm going to say them, and then you'll get to say them, and then we'll talk about what they mean.








So we've been looking at particles all through this unit, and they're anything that has mass.

Everything is made up of particles.

A substance can either be soluble or insoluble.

If it's soluble, that means it will dissolve like sugar is soluble.

If you mix sugar into water, it dissolves, and insoluble means it won't dissolve.

So, something like sand is insoluble.

If you put it into water, it doesn't dissolve.

Then, the three words on the bottom, we looked at in our lesson on dissolving.

So, the solute is the solid that you start with.

So, in the example of dissolving sugar and water, our sugar would be the solute.

The solvent is the liquid that you start with.

So, in that example, it would be the water, and our sticky way of remembering that is that solvent has a V in it for vase.

You keep water in vases.

So, the solute, which is the solid.

The solvent is the liquid.

When you mix them together, you get a solution, which is the answer.

That was our sticky way of remembering that, okay? In today's lesson, we're going to start with some recap, although we've already started recapping with our star words, then we're going to look at three methods for separating mixtures, sieving, filtration, evaporation, and then at the end, we're going to plan an investigation or choose the best method for something.

Let's start with our recap.

We are really good at solid, liquids, and gases now, but just a quick exercise to not only send blood to our brain, but remind us how particles in solid, liquids, and gases move.

Can you show me your actions for each of these? So, see if you can remember without me showing you first.

Show me your action for solid.

So, remember, your hands are the particles.

Show me your action for liquid.

And show me your action for gas.

Great, so for liquid, we should have our particles closely touching and vibrating on the spot.

Did I just say for liquid? I wasn't even trying to trick you there.

Just a slip of the tongue.

For a solid, we should have our two particles touching, and vibrating next to each other.

Show me your action for solid.

But only if you remembered it.

For liquid, we should have our particles touching, but sliding past each other.

Show me your action for liquid, and for gas, get ready to go fast.

We should have our particles far apart and moving really quickly past each other.

Show me your action for gas.


Well done if you remembered those.

Okay, now, this bit of recap is a little bit trickier.

Think about our star words here.

So, this is a diagram of one of the experiments that we did last lesson.

So you've got sugar being added to your water, and creating sugar water, and you can see that the particles are being shown there.

Can you please label, A, B, and C? Which was the solute, which was the solvent, and what's the solution, please? Pause the video and write down for me now.

Great, so A is our solute, B is our solution, and C, sorry.

Gosh, I'm really tripping over my tongue today.

I'm going to focus.

A is our solute, B is our solvent, with our V for vase, and C is our solution.

It's what we end up with, and you can see from the particles, we've got our solid particles in A, our liquid particles in B, and then in C, our solid has dissolved.

So we've got one solid particle.

It's still there, but now it's surrounded by the liquid particles, so it's hard to see it.

Let's take a look at our first method of separation today.

So, this is sieving, and here's a picture of some sieving going on.

Sieving is used to separate an insoluble solid from a liquid when the solid particles are large.

So, in this picture, our large solid particles are rice that are being separated from our liquid, water.

It's being sieved probably for somebody's dinner.

During sieving, the mixture is passed through a wire mesh.

The wire mesh has holes in it, which are big enough for the liquid particles to pass through, but they're small enough to stop the large solid particles from passing through.

And at the end of separation, what we're left with is the solid left in the sieve.

Okay, so the main point there is sieving is used with insoluble.

That means they don't dissolve, large solids, insoluble large solids.

What's it used for? Insoluble large solids.

Great, okay, like our rice.

Our rice is large, and it's insoluble.

It doesn't dissolve in water.

Let's test your memories.

What is sieving used for? Write down the answer for me now, please.

Great, let's check your memory.

Sieving is used to separate an insoluble solid from a liquid when the solid particles are large, okay? Or you could have written that in different wording and said, sieving is used to separate an insoluble and large solid from a liquid.

Okay, the key things there are that we're separating a solid from a liquid, and that our solid is insoluble and large.

So if you've included the words insoluble and large, then you can underline them, give yourself a tick, and if you haven't, that's okay, but could you go and add them in in your different coloured pencil for me now, please? If you need some time to edit, just pause the video here.

Great, the next method we're going to look at is filtration, and I'm going to show you what this one looks like first.

Here, I have a glass of water that's got sand in it.

So I've got a liquid and an insoluble solid.

You can see the sand at the bottom hasn't dissolved.

It's insoluble, but the difference here is that my sand is really small pieces of a solid.

So if I were to try and separate this with sieving and pour it through a sieve, my water and my sand would just go through the gaps.

It's too small, so we use a different method, called filtration.

Okay, so for filtration, you need a cup or a container at the bottom to catch the water that's going to come through, and then you need a funnel, which is what will funnel the water through as I pour it, and the most important thing you need is filter paper, okay? So this is filter paper that's in a cone shape.

I'm going to open it up like this.

I'm going put it in my funnel and I'm going to pour my water and my sand mixture through it.

Okay, I'm just going to mix up before I do, so that I don't get all the sand left at the bottom, quickly, and I'm going to pour it into here.

So, I'm spilling some water, of course.

Watch out, it's just a glass.

It's not made for pouring.

You can see that coming through this filter paper is completely clear water.

If I compare the two colours, this one is much lighter than this one, and I'll show you what's inside the filter paper in a second.

Okay, so it's still dripping through.

So we're just going to give it some time to finish dripping through.

And some of the water has soaked into the filter paper, but the majority of it is in this glass.

Then, I'll show you what is in the top of the filter paper now.

So, here, it's a bird's eye view of our filter paper.

You can see there's still a little bit of water trickling through here, but we have our sand that has been caught in the filter paper.

So this is all the sand that's been stopped by the filter paper.

So we've separated our liquid, water, from our.

Did you just see me pour that out? Ah, I'm too impatient, just let it finish.

And now I've made my desk quite wet.


Here, we separated our liquid, water.

Most of it ended up in this glass.

Some of it got on my desk.

And our insoluble, small solid, our sand here in the filter paper.

I'm going to clean up now.

Here is a diagram representing the demonstration that you just watched.

So, filtration is used to separate an insoluble solid from a liquid.

So, same as sieving, but the difference here is that that insoluble solid also needs to be really small.

If we were to use sieving in this scenario, so with a small solid like sand, it wouldn't work, because the sand would just go through the holes in the sieve.

In filtration, we pass the mixture through a piece of filter paper, and the filter paper has teeny tiny holes in it, which are big enough for the liquid particles to pass through, but small enough to stop the solid particles from passing through, and at the end of the separation, the solid is left in the filter paper.

The solid is left in the filter paper.

In this case, it was sand that was left.

This is a diagram that I have drawn to show you what the particles would look like in our mixture of sand and water before we separated them.

So, you can see, we had your liquid at the top and your sand collecting at the bottom.

That's what my cup looked liked until I kind of gave it a mix, and then your particles would have, you'd have your liquid particles on the top, and then your regular arranged solid particles on the bottom, okay? It looks different to what we're going to look at next, or when they're soluble particles, 'cause if it was a soluble particle, those darker solid particles would all be separated, but when they're insoluble, they just float to the bottom.

Okay, can you please answer the question? What is filtration used for? So, think about, what's the key difference between this and sieving? Pause the video and answer this question for me now, please.


Let's check your answers.

So, filtration is used to separate an insoluble solid from a liquid when the solid particles are very small.

Okay, so again, the key point here is the separating solid from liquid, but the solid needs to be insoluble and very small.

So, just like last time, can you make sure that you've included the words insoluble and very small? If you have, give yourself a tick next to those two words.

If not, underline them.

If you haven't, could you add them in in your different colour, please? Pause the video if you need time to edit.


Let's look at our third method of separating.

So, this one is evaporation.

There's a diagram here that shows you how evaporation occurs, but I'm going to explain each part so that you understand what's going on.

So, on the top, we have a dish that has water, a mixture of water and a soluble solid.

So that could be maybe sugar water or salt water.

We know that both sugar and salt are solids that dissolve in water, so they're soluble.

That dish of, let's just say it's salty water, for this example, that dish of salty water, that mixture is sitting on top of a stand, a tripod is what we call it, but it's effectively a stand, and then underneath that arrow is representing heat.

So it's a science diagram that's normally used to represent a Bunsen burner, which produces a flame, okay? But you can just think of it as heat.

So, evaporation is used to separate a soluble solid from a liquid.

In evaporation, the solution is placed in an evaporating dish and heated using a Bunsen burner.

The liquid solvent, so the water in this case, evaporates, leaving behind solid crystals.

So, in our example, it would leave behind crystals of salt.

What is evaporation used for? Can you pause the video and answer this question? Think about how it's different to filtration and sieving.

Evaporation is used to separate a soluble solid from a liquid.

Okay, so that's the key point here.

It's a soluble solid like salt or sugar from a liquid.

Now, you can actually try this yourself at home.

However, not with a Bunsen burner or a flame.

You can try this experiment as long as you have enough time to do it.

So, if you get a dish, so the shallower it is, the better, really, a bowl would do, but a shallow dish is even better, and you put in it water and lots of salt and you mix it around and you let all the salt dissolve, and then you leave it, preferably somewhere warm and sunny.

So maybe by a window and leave it for a couple of days.

You'll find that the water evaporates and you're left with salt.

Okay, so that's something that you can try yourself at home.

Okay, next, I would like you, please, to complete this diagram.

So this is.

Oh, don't do that.

Next, I would like you to help me complete the particles on this diagram.

So let's just think about it before you draw your particle diagrams. In A, we have a solution.

So we've got our salty water.

What do the particles look like in a solution? We have revised this, this lesson, so if you're still not sure, go back and have a look at our recap section at the beginning.

Okay, remember, it's a solid dissolved in a liquid.

So think about what your particles are going to do there.

Then for B, you've got your solid left over in a dish.

So you can have solid particles, and in C, you've got your water that's evaporated.

Because it's evaporated, what state of matter are those particles going to be? When something evaporates, is that a solid, a liquid, or a gas? What's the end product of evaporation? It's gas.

Okay, so it's going to be water vapour particles that you're going to draw.

Can you pause the video and have a go at drawing these particle diagrams for me, please? Great.

Let's check.

So, A would look like this.

You've got your water particles, but then you've got one or maybe two particles of solid surrounded by them.

Then, B, you've got your solute, your solid that's leftover in that evaporating dish.

So, your salt crystals.

So you're going to draw solid particles, all lined up and really close to each other, and then for C, we've got your water vapour.

So you've got your blue water particles again, but they need to be far apart from each other, because they are now a gas.

If you need to mark your work, correct your answers, pause the video and do that for me now, please.

That was a tricky question, so well done if you've got it right.

If you've made a mistake, not a big deal at all.

You've got the answers now to correct your answers.

Okay, the next thing we're going to do is choosing the correct process.

So, we've learned about sieving, evaporation, and filtration today, and you should, hopefully, on your sheet of paper, have written down exactly what we use those three for.

So, if you need to, you can go back and check your notes.

I'm going to give you some scenarios, and I want you to tell me which method you would use to separate them.

So, think, each time, is it a soluble solid or an insoluble solid? And if it's insoluble, is it big or small? So which would be the best method to use? Number one, to remove soil from a sample of river water? Number two, to separate rice from water? And number three, to isolate crystals of copper sulphate from a solution of copper sulphate in water.

Number three is quite tricky, but the key there is that it's a solution.

So, if it's a solution, is it soluble or insoluble? Have a think about it.

Pause the video, and complete those questions for me now, please.

Okay, let's check your answers.

So, for number one, the best method for separating river water from soil would be filtration, okay? Because soil is insoluble, but it's very small.

Number two, the best method for separating rice from water would be sieving, because rice is insoluble and it's big.

You could technically use filtration to separate rice from water.

A filter paper would also stop the rice and let the water through, but sieving is a much quicker method.

You saw when I was doing my demonstration of filtration, that actually can take quite some time for the water to slowly drip through the filter paper.

So, if you're making rice for your dinner, you might not want to wait that long.

You might get impatient like I did and spill water everywhere.

So, sieving is the quicker option, and number three, because you have a solution, because the copper sulphate is dissolved, then you need to use evaporation in order to do that, and you're left at the end with copper sulphate crystals in the bottom.

They're really bright blue crystals, which at some point during your school career, you will get a chance to see.

Okay, now, I've got a question for you.

This time, we're going to have to choose two processes.

So, out of evaporation, filtration, and sieving, we're going to have to do two of these, one and then the other.

So how could you separate a mixture of sand, stones, and water? So you want to have separate sand, separate stones, and separate water, to produce three pure samples at the end.

What would your two steps be? Have a think and write them down for me please.

What would you do first? Okay, so first, you would use sieving to separate the rocks from the sand and water.

So that's what you do as the first step.

You take the biggest solid out.

Then you could use filtration to separate the sand from the water.

That would be the most efficient way to do this.

Okay, you can also see that I've written this a bit like a method, so I've written numbers and I've used first-up verbals in order to give structure to my order.

So, I've used "first, comma, next, comma." Can you please take this opportunity to pause the video, and with my answer on the screen, can you edit or make your answer better? Whether that's writing a full sentence, adding that first-up verbals on the front, adjusting your language, or maybe correcting the method that you've used.

Pause the video and do that for me now, please.


That brings us to the end of our lesson.

Well done for all of your hard work today.

I hope that you are proud of what you have accomplished.

If you would like to share your work on Twitter, then you can ask your parent or carer to do that for you with the hashtag "#LearnWithOak." I hope you have a fantastic rest of your day, and I will see you back here for another science lesson soon, I hope.

Bye, everybody.