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Hello, my name's Mrs. Nevin, and today we're going to talk about representations of a mole as part of our unit on calculations involving masses.

Now what we'll do in today's lesson, you may have some experience of from your previous learning, but really what today is about is being able to not only answer that big question of what are substances made of, but also for us to see that interconnectedness of some of the mathematical relationship we've learned so far in this topic.

And also to see how we can use those relationships to better visualise representations of moles of different substances.

So by the end of today's lesson, you should be comfortable accurately representing a set number of moles of various substances.

Now, throughout the lesson, I'll be referring to some keywords, and these include mole, interconversion, accuracy, apparatus, and uncertainty.

Now the definitions for these key terms are given in sentence form on the next slide, and you may wish to pause the video here so you can jot down a quick note of what each represents for reference later on in the lesson or later on in your learning.

So today's lesson is broken into two parts.

The first we'll look at how we can calculate different masses and volumes using those mathematical relationships we've learned thus far.

Then we'll move on to look at how we can consider the best way to use laboratory equipment in order to create a mole show.

So let's get started by looking at how we can calculate masses and volumes.

Now the thing to remember is that chemists refer to different substances by their particles.

And because particles are so small, we tend to package them up into this idea of a mole.

So one mole is equivalent to 6.

02 times 10 to the 23 particles of a particular substance.

Now particles are too small and it's too laborious to try and count them all up.

So we use a mathematical relationship in order for us to be able to calculate how many particles we have of a particular substance in a sample.

And that mathematical relationship is this, that the mass in grammes of a substance is equal to the number of particles, the number of moles times that substances relative formula mass.

It's a really important equation.

It's one that I would highly recommend that you spend time memorising.

Okay, now, chemists use this relationship to interconvert between these variables.

So what do we mean by interconvert? So if we break this word apart, the prefix of inter simply comes from the Latin that means between and convert means to change.

So when we bring these two parts of our word together, it simply means to change between things.

So in chemistry, what we're doing is we're actually changing between the different units, within that mathematical relationship using a comparison standard.

Now this is incredibly important.

The ability to interconvert a mathematical relationship is a really fundamental skill for chemists because these mathematical relationships represent an arsenal of relationships that we can tap into whenever we need to in order to find an unknown.

Now, if we take a closer look at that mathematical relationship of mass equals moles times relative formula mass, what that means is the number of particles in one mole will never change.

It doesn't matter if you've changed substances.

One mole is always equal to 6.

02 times 10 to the 23 particles, but the mass representing that number of particles of a particular substance will change.

And it changes because these substances have different relative masses.

For instance, if we look at just an atom, so something like xenon, one of our noble gases, its relative masses is going to be its relative atomic mass, and that's 131 straight off the periodic table.

If we look at a molecule now, so this time we're looking at water, it has a formula of H2O and its relative formula mass then will be 18, simply adding up the relative masses of the atoms that make up that molecule.

If we look at a formula unit then, so we're looking at something that is an ionic substance, it's relative formula mass is equal to the relative atomic masses for those ions that make up that formula unit, in this particular example.

So for sodium chloride, it's 58.

5.

Now this picture shows a one mole sample of four different substances.

So we're talking about in each one of these samples there is 6.

02 times 10 to the 23 particles of that substance.

And the substances we have then are sugar, copper sulphate, sodium chloride or basic table salt and water.

Now, if you look more closely at the relative formula masses, as we move from left to right, those relative masses are going down, they are decreasing and if we remember our mathematical relationship, the mass in grammes is equal to the number of moles times that relative formula mass.

So as the relative masses are going down, so is our sample size that represents the exact same number of particles.

So this relationship allows chemists to exploit it for the interconversion it allows, okay.

As long as I have at least two pieces of information needed for this relationship, I can find the third, I can find an unknown, and that could be the mass in grammes, the number of moles in a sample or even the relative formula mass for an unknown substance.

So, where am I gonna get these two pieces of information? Usually it's going to be the mass that you've managed to measure out on a balance in the laboratory and the relative formula mass you can always find because all you need to do is have that chemical formula and a periodic table and a calculator handy.

So ultimately this is your go to interconversion mathematical relationship.

Mass in grammes is equal to moles times relative formula mass.

So let's have a go at using that relationship to do some interconversion.

I'd like to know the mass of 0.

25 moles of ethane, which has a chemical formula of C2H6.

Now because I need to know the mass, the equation I'm using is mass in grammes is equal to moles times relative formula mass or Mr. Okay, now I have the number of moles it was given to me in the question, 0.

25, but I need to find one other piece of information and the easiest one to find is that relative formula mass because all I need is a periodic table and a calculator and I've been given the chemical formula.

So when I find that, its Mr or relative formula mass is 30.

All I need to do now is pop those numbers into my equation to interconvert to mass.

So mass is equal to 0.

25 times 30 and that gives me 7.

5 as an answer.

This means then that not 0.

25 moles of ethane will have a mass of 7.

5 grammes.

What I'd like you to do now then is to calculate the mass of 1.

3 moles of linalool, which has a chemical formula of C10H18O.

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

Okay, let's see how you got on.

So if you have managed to calculated it correctly, you should have reached a final answer of 200.

2 grammes of C10H18O that linalool.

Now if you didn't get that answer, what I'm gonna suggest you do is pause the video and take a closer look at the working out to see where you may have gone wrong so going forward we can fix those mistakes.

But very well done if you manage to get that final answer of 200.

2 grammes.

Good job guys, great start.

Now at room temperature, many substances exist as a liquid, particularly ones that are used by chemists.

Now, a physical property of any pure substance is its density.

Now density, if you remember, is the amount of matter that can fit into a defined space and it's calculated as mass divided by volume.

Now because of that, it has the standard unit of grammes, centimetres to the minus three or grammes per centimetre cubed.

So that's a mass divided by a volume unit and we can represent that unit in a slightly different way, which looks like a fraction which is grammes divided by cm cubed.

So chemists are able to exploit this mathematical relationship in order to interconvert between some really useful units of volume and mass.

So if I look at my equation here, I have density is equal to mass divided by volume.

If I multiply both sides of my equation by volume, I get a new mathematical relationship where mass is the subject.

So the mass in grammes is equal to the density times volume.

So I can go from density to find the mass of a substance.

Likewise, with this equation, if I was to divide it by density on both sides of that equation, I get a new mathematical relationship where the subject is now the volume.

The volume of a substance will be equal to the mass divided by the density.

So why go through all these interconversions? What is the point of it? Well, if you take a closer look at those last two mathematical relationships, the mass and the volume are two things that can be really easily measured using equipment in the laboratory, the mass in grammes, and the volume in either centimetres cubed or decimeters cubed.

So we now have a way to use units in order to make really easy simple measurements within the chemical laboratory.

Now, if we're going to be making those measurements in the laboratory, we first need to make sure that we're doing the interconversion correctly.

So what I'd like you to do is tell me what is the mass of 10 centimetres cubed of bromine given its density is 3.

1028 grammes per centimetre cubed.

And I'm gonna give that answer to three significant figures.

Okay, well I know I need to find the mass.

So the relationship I'm using is mass is equal to volume times density.

Now some of these words start to get a little muddled up.

So what I'm gonna do is put the units for each below because sometimes when you're given lots of different numbers, it can be really easy to put them in the wrong place, you're not quite sure where to put them.

So let the units guide you.

Okay? So the volume then is centimetres cubed.

So the number I'm going to be using here is 10.

The density remember is grammes per centimetre cubed.

So that value that I need to put into my equation is 3.

1028.

So if I put those values into my equation, I get a value of 31.

028.

But remember my final answer needed to be to three significant figures.

So my final answer for the mass of 10 centimetres cube of bromine is going to be 31.

0 grammes.

What I'd like you to do now then is to use this guide that I've given you on the left to tell me what is the mass of 15 centimetres cubed of mercury given its density as shown.

And don't forget to give your answer to three significant figures.

So you need to grab that calculator, pause the video, and come back when you're ready to check your answer.

Okay, let's see how you got on.

So if you've done all your calculating correctly, you should have got a final answer of 203 grammes of mercury is equivalent to 15 centimetres cubed of mercury.

Now if you didn't get that answer, please pause the video here so you can double check your processing so that we can try to avoid those errors going forward.

So very well done there if you managed to get that correct.

Great job guys.

Okay, let's try another one.

I'd like to know what the volume of 15 grammes of sea water is going to be given that its density is 1.

03 grammes per centimetre cubed.

And I want to continue giving those answers to three significant figures.

So same as before, I need to get a mathematical relationship written down.

And because I'm trying to find the volume, it's going to equal mass divided by density.

And again, as before, I'm just gonna jot down those units to help guide me in terms of where to put my different numbers.

So the mass is 15 grammes and the density, because are units are grammes per centimetre cubed is 1.

03, when I calculate that out, then I get an answer of 14.

563, but to three significant figures then tells me that 15 grammes of seawater will have a volume of 14.

6 centimetres cubed.

What I'd like you to do now then is similar as before, use the left hand side as a guide and tell me what do you think the volume will be of a 27 gramme sample of benzene given its density is not 0.

8765.

And again, please give your answer to three significant figures.

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

Okay, let's see how you got on.

So if you've done all your calculations correctly, you should have a final answer of 30.

8 centimetre cubed of benzene is equal to a 27 gramme sample of it.

And again, as before, if you didn't get this answer, please pause the video so you can take a closer look at that working out to find out where you may have gone wrong in your calculations.

Remember guys, it is absolutely essential that you're showing you working out so that we can find any errors as we go forward.

So please make sure you are doing this, but very, very well done if you manage to get that correct.

Great job, guys.

Okay, time for the first task of the lesson.

What I'd like you to do is to complete the table below and you're going to give the masses in the final column to three significant figures.

My recommendation is that you work with people nearest you and double check that you have the formula correct for each substance before going forward with your calculations.

This is gonna take a little bit of time.

You definitely need a calculator and a periodic table and possibly some scrap papers so you can write out your workings out as well.

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

Okay, let's see how you got on.

Now what I'm going to do is recommend that anytime you are being asked to calculate something that you include the equation that you're using somewhere, I always find it handy to have it written at the top of a paper anyway, just so you can quickly remind yourself what you're using 'cause things start to blend together after a while.

The equation you're using here is mass in grammes is equal to the Mr or relative formula mass times the number of moles.

So for sodium chloride you were given the formula and your mass then should be 87.

8.

What I'm gonna do for the rest of these substances is just give you that final answer and if at some point, you've gone wrong, that's when you want to pause the video, double check.

Perhaps you've got the relative formula mass incorrectly and it might be that you have written the formula incorrectly, so just double check things as you go ahead.

So for water, you should have had 27.

0 to three significant figures.

Zinc was 97.

5, sodium hydrogen carbonate is 126, sulphur was 48.

0, and ethanol should have a mass of 69.

0 for a mass of 1.

5 moles sample.

Well done if you managed to get those correct.

Right, for the second part of this task, I'd like you to use the data that's been provided to calculate either the mass or volume for each of these substances and to give your answers to three significant figures.

So we're really practising that interconversion, that ability to move between different units and you might need to be using different equations.

So always double check what information do you have, what information are you being asked to find, what equation are you going to need, what mathematical relationship are you going to need in order to answer that question.

So 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 this first example, I'm going to go through the answers slowly so you can see how I came about doing my working out.

And then for parts b through d, I will simply give you the final answer and you can pause the video to double check your workings out if you'd like.

Now for the part a, I've been asked what is the mass of 15 centimetres cubed of ethanol and I've been given the density of it.

Now because of that, I've been given a volume and a density.

I know that I am not using mass equals Mr times moles because even though I've been asked to find the mass, the details that I've been given don't match that mathematical relationship.

I have to use a mathematical relationship that works with the values I've been given.

And because of that, my mathematical relationship here is gonna be mass equals volume at times density.

So my volume was 15 centimetres cubed, the density was not 0.

7892 grammes centimetre cube.

When I multiply them together then, I get a value of 11.

838, but I was asked to give my answer to three significant figures and because of that my final answer will be 11.

8 grammes of ethanol.

So well done if you got that correct.

So for part b, I was asked to find the volume of octane.

So I'm using the relationship mass divided by density.

Then given the mass and the density and when I process it, I should have a final answer of 356 centimetres cubed of octane is equal to a 250 gramme sample.

For c, I was also asked to find the volume.

So again, my relationship is mass divided by density.

I have my two values for mass and density, and when I divide them I get a final answer of 12.

3 centimetres cubed, which is an answer to three significant figures.

So well done if you managed to get this one correct.

And for d, again, I've been asked to find the mass and because of the information I've been provided in this particular question, I need the relationship of volume times density.

So those are my values that have been given in the question, and when I calculate it out, I get a final answer of 12.

5 grammes of 20 degrees Celsius water will take up a volume of 12.

5 centimetres cubed.

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

Great job.

Now that we're feeling a little more comfortable being able to calculate the mass or volume of different substances, let's look at how we can take those relationships together and our understanding of equipment to create a mole show.

Now, one of the reasons that all of these interconversions via mathematical relationships is done is because chemists rely upon them in order to ensure that we have accurate measurements being made during investigations.

For instance, we said earlier in the lesson that the mass in grammes is equal to the number of moles, the number of particles times a relative formula mass, but also there's another relationship involving mass in grammes and that's the density times the volume of a pure substance.

So we have two different mathematical relationships both giving us a value for one unit and that's the mass in gramme.

So we can use those two in order to get an accurate measurement.

But these relationships then also ensure an accurate measurement of the number of particles that are either used or produced in a chemical reaction.

And that's more important because if we can keep track of those individual particles, we have far more accurate understandings of what's going on within a reaction.

And the number of particles, if you remember, is equal to the number of moles times that packet value of 6.

02 times 10 to the 23.

And if we look at that, again, we have moles.

So we have two different relationships that help us to get to the mass that helps us to find the moles, that helps us to find the number of particles.

So there's all these different mathematical relationships that we can use in order to keep track of those all important particles in a reaction.

The thing to remember though is that interconversion with these mathematical relationships only ever works if the units match.

So let's look at a few examples.

If I were to multiply these units together, the grammes would cancel out and I would be left then with that single unit of centimetres cubed over one or just centimetres cubed.

That would work.

For this other one, I still have units for mass kilogrammes in grammes, but they're different.

A kilogramme is a thousand times larger than a gramme.

Those units are not the same and therefore, this interconversion would not work.

Again, I've got an example here this time using volume units, I've got decimeters cubed.

Now they're the same, I would cancel out and that would give me that single unit of grammes over one or just grammes.

So again, that would work.

Here, I still have units for volume, but one's decimeters cubed and one is centimetres cubed.

They're not the same.

And because of that, that particular interconversion would not work.

Now if a unit doesn't match, what you could do is change it accordingly before continuing on with your interconversion in order for you to get an accurate value for whatever you are trying to find.

But it is absolutely essential that the units match.

So let's stop here for a quick check.

Which interconversion shown below will cancel out to a single unit? And if you figured that out, what do you think that single unit might be? Well, let's take a look at these.

For a, I have hours and minutes.

They're both units for time, but they're different.

Okay, so that wouldn't work.

For b, again, I still have millimetres, but one is cubed and one is squared, one is an area, one is a volume, and therefore those units are not the same and it wouldn't work.

For the bottom one for c, well done if you chose that because I have metres cubed, sorry, metres squared and metres squared, they would cancel out.

And so my final single unit would've been a Newton.

So very well done if you chose c, and excellent job, if you also managed to identify the single unit, it would cancel down to which is a Newton.

Well done, guys.

Now how we interconvert between the substances to the number of particles we have in a sample depends on the type of substance that you're using.

If you have a solid substance, the easiest thing to do is going to be to measure that mass of a substance on a balance.

At that point then, when you have the mass in grammes, you can interconvert to the number of moles using that relationship of moles is equal to mass divided by the relative formula mass of the sample that you are looking at.

At this point then, you can interconvert to determine the number of particles in that sample if you'd like to or if you're being asked to.

Normally chemists would like to keep that final answer in moles because the numbers are smaller and they're a lot easier to wrap your head round and the maths is a little bit easier.

But you could then find the number of particles is equal to the number of moles times that conversion is 6.

02 times 10 to the 23.

To find the number of particles in a liquid substance, you're gonna have to do something slightly different.

You'd probably use a measuring cylinder to measure out the volume.

At this point then, you could interconvert using the density of that substance to find the mass and then interconvert again to find the number of moles in that sample.

At this point then, like before you could interconvert to find the number of particles.

So ultimately what we have through these mathematical relationships are kind of pathways that we can use to get from one place to another to try and answer an unknown given the information available to us at that time.

So there isn't always a one way to do things, but what you have then is an arsenal of pathways that you can follow to get from one end to the other.

Now what you may have noticed in those previous slides about the solids and the liquids is that each of these interconversions rely upon a measurement.

So the start of our pathways starts with a measurement and scientists aim to use the most appropriate apparatus for those measurements in order to minimise the uncertainty of the measurement.

Now they do that by ensuring that the apparatus is both the appropriate size for what they're trying to measure and the appropriate resolution.

And the key here is not only to have an accurate measurement, but also so that you can perform that measurement safely.

So in general, an apparatus that has more markings, has a higher resolution and a lower uncertainty.

The higher resolution that you have on an apparatus tends to lead to more precise measurements.

So we're looking at something that has maybe more decimal places and more precise measurements also leads to a lower mean uncertainty.

So an overall average uncertainty that you have if you have multiple measurements.

Let's stop here for a quick check.

Which apparatus shown do you think has the highest resolution? Well done if you said c.

Remember, resolution is the number of markings we have between labelled numbers on an apparatus.

And when we look at these, we can see that c, there's only one number between the labelled markings on it and that there are actually 10 markings between those two numbers and therefore, c shows the highest number of markings between those labels.

It has the highest resolution.

Well done if you chose c.

Now regardless of the apparatus that's used, there's always going to be a bit of uncertainty, a bit of doubt about the accuracy of a measurement that we get using that particular apparatus because we'll be wondering is it actually on that resolution marking or is it between those markings? So we can actually calculate the uncertainty for a particular piece of apparatus by taking its resolution and dividing by two.

And the uncertainty then for that measurement is given as a plus or minus marking for it.

So that plus or minus is giving us a range within which we can find an accurate measurement for whatever we're trying to measure.

So I have here two rulers.

They both are able to be used to measure the length of something, but one obviously has more markings or a higher resolution than the other.

That's the one on the right.

Now their uncertainty then for the one on the left is plus or minus 0.

05.

So the range is within two decimal places, whereas for the one on the right, the uncertainty is plus or minus 0.

025 centimetres.

I have a much smaller range within which I can find that accurate measurement.

So my choice of equipment is going to be impacted by the resolution, which impacts essentially the uncertainty of the measurement that I am making using that piece of apparatus.

And the key thing to remember on the choice of apparatus is that if you have to use it more than one time, you are multiplying then the uncertainty that you have for your measurement.

Okay, so even if something has a higher resolution, if you've gotta use it lots of times in order to get that final measurement, you are multiplying your uncertainty the number of times you have to use it.

So you've gotta be really careful on the piece of equipment that you were choosing in order to make a measurement.

Let's stop here for a quick check.

Which apparatus shown do you think is most appropriate for measuring out 2.

3 grammes of copper turnings? Well done if you chose b.

There might have been a temptation to choose a because it has the most number of decimal places, but we're talking about most appropriate.

So we're looking at the size of the measurement that we need to be taking because we only need a measurement to one decimal place, the resolution matches it and therefore, the most appropriate resolution here is going to be b, to one decimal place.

Well done if you chose b.

Let's try another one.

Which apparatus here do you think is most appropriate for measuring out 1.

5 centimetres cubed of sulfuric acid? Well done if you chose a.

10 centimetres cubed is not going to be appropriate because it's very difficult to get to 0.

5 centimetres cubed if it's resolution is a 0.

2, even numbers versus odd numbers.

So c is out.

For b, it would work.

However, you'd have to use this piece of apparatus more than once.

And not only are you increasing the uncertainty, but you're also increasing the chance for error with that.

A is most appropriate because you will definitely be able to measure to 1.

5 centimetres cubed and I only need to use it once.

So it's the most appropriate measuring device here.

Well done if you chose a.

Okay, one more.

Which apparatus is the most appropriate for measuring eight centimetres cubed of water? Well done if you chose c.

Now I could have used any of these to measure out eight centimetres cubed.

It's just that if I use that 10 centimetre cubed measuring cylinder, I can get bang on that 8 centimetre cubed mark and I only need to use that apparatus once.

So I'm keeping that uncertainty and chance for error as minimal as possible.

So c is the best answer.

Well done if you got that correct.

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

What I'd like you to do here is something very similar to what we did in task A.

I'd like you to calculate the mass of different samples.

But this time we're gonna use 0.

1 moles of a sample rather than 1.

5 moles of a sample.

Now, I want you to, as before, give your answer to three significant figures and you may wish to use some of the information from task A part one to help you go a little bit faster on this task if you choose to.

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

Okay, let's see how you got on.

So as before, I'd always recommend that you are writing out the equation that you're using that mathematical relationship.

And for this one it's the mass in grammes equals moles times the relative formula mass for your substance.

And if you've done all this correct, the working outs should give you these answers.

So I'm not gonna read them all out.

If you'd like to just pause the video and double check your answers and for any that you got incorrect, maybe go back and double check you have the relative formula mass correct and the correct formula.

Now the eagle eyed among you may have seen that in part one we had two liquid substances that were listed.

So what I'd like you to do now is to use the information from task B part one and the data that's been provided below to calculate the volume that will represent a 0.

1 molar sample of each of these substances, and to give your answer to three significance figures.

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

Okay, let's see how you got on.

So for this question we needed to use the mathematical relationship of volume is equal to mass divided by density, and when we use that, we get a volume of 1.

80 centimetres cubed of water and 5.

83 centimetres cubed of ethanol.

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

Great job, guys.

For this final task then what I'd like us to do is to use the mass in volumes that were calculated in tasks B parts one and two to complete the table below.

Principally you're gonna be using those calculations to fill in that first column of the mass or volume that's needed to represent 0.

1 moles of a sample of each of those substances.

Then what I'd like you to do is to consider what do you think would be the most appropriate apparatus that you could use to measure out those masses or volumes to represent a 0.

1 mole sample.

Once you've done that, you then will have a table completely laid out that you can use to do part B of this task, and that's to create a display of a 0.

1 more sample of each of the substances in that table.

So this is gonna take a little bit of time, so pause the video and come back when you're ready to check your work.

Right, let's see how you got on.

So for that first column with a massive sample, all you needed to do was to copy over your answers from task B, parts one and two, depending on whether or not it was a solid for your masses or a liquid for the volumes.

What I really wanted you to do the most of for this part of the task was to really discuss what do you think would be the most appropriate apparatus to use to measure out each of these masses or volumes so you could get the most accurate measurement based on those values.

And I've given you a little bit of a guide with the sodium chloride.

Because the mass goes to two decimal places, we'd also would like a balance that goes to two decimal places as a minimum.

When you have a volume, you have quite a few more options open to you.

This water going 1.

80 centimetres cubed, you could have used a syringe, but you might not have a syringe available at the lab, in which case you need to use the next most appropriate apparatus.

Perhaps you need to use a dropping pipette instead multiple times, or perhaps you have a five centimetre cubed measuring cylinder that you could use once that will allow you to get to these values.

You're gonna have to use what's most appropriate in terms of what is available to use.

But hopefully this task stimulated a little bit of discussion about what was available and what would be most appropriate within those available pieces of equipment.

For the zinc, the sodium hydrogen carbonate and the sulphur, because these also go to two decimal places, you would use a two decimal place balance just like we did with the sodium chloride.

And the same conversation could have been had about the ethanol like we did for the water.

Perhaps use a syringe, maybe use dropping pipettes or a measuring cylinder to do the best you can because ultimately we're looking to find the apparatus that's gonna allow us to have the most accurate measurement to represent these different substances in our display.

Now, once you have made those decisions, you needed to then take it all together to create a display of the different samples.

Now, your display may look something like this, but what I would hope that you included in your display then was that you'd labelled each substance so we know what is in each one of these different containers that you are also showing the mass or the volume of those labelled substances.

Because honestly, that would allow then any of your peers to double check your work.

And that's what any good scientist would want is somebody to double check their work.

And if you really wanted to stretch yourself, maybe you've included the uncertainty and the measurement of your mass or volume of your display so that we can take into consideration then the resolution of your apparatus choice as well.

So, very well done if you manage to create a display and add all those things in it.

I hope this has helped you to gain a better appreciation for that interconnectedness between the number of particles, the moles that we're talking about, the mass or the volume of that substance and its formula.

Wow, we have done a lot in today's lesson.

So let's just take a moment and summarise what we've done today.

Well, we've learned that interconversion, so moving between units like grammes, moles, volume, density, particles, being able to move between them is a really fundamental skill in calculations and particularly in chemical calculations.

We've also realised that if we are gonna interconvert successfully, the units need to be the same in order for us to cancel them out to get that final single unit that we need when we're interconverting.

We also took a look at apparatus and how manipulating the apparatus correctly helps to make sure that any measurements we're making are accurate and that we're being safe in the lab as well.

So we're reducing the number of times we need to use a piece of apparatus, and we're making sure that it won't overflow, for instance, if we're taking the measurement of a volume.

But we also looked at that choice of apparatus and that it's the most appropriate one for that particular measurement we need to make so that we're reducing the uncertainty to ensure that accuracy and the measurement that we're making.

It's a really important but overlooked skill.

And I hope that today has given you a little bit more of an experience of thinking about that interconversion and it's linked to what we're doing in the lab.

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

I've certainly had a good time learning with you, and I hope to see you again soon.

Bye for now.