Hello, my name's Mrs. Nivin, and today we'll be looking at a solubility practical as part of our topic on solutions.

You may have done something similar in some of your previous learning, but what'll we do in today's lesson will help you going forward in your journey through science as you conduct more practical work.

It will also help us to gather some evidence that's going to help us answer that big question of how can we explain how substances behave? So, by the end of today's lesson, you should be able to carry out a fair test that investigates solubility.

But more than that, be able to record the measurements that you make in an appropriate table of results.

Throughout the lesson, we'll be using a variety of keywords, and these include dissolving, solubility, variable, table of results, and anomalous.

The definitions for these keywords are on the next slide in sentence form, and you might find it useful to pause the video here to read through those and perhaps make a note of them so you can refer to them later in your lesson.

So, throughout today's lesson we'll be looking at three main things.

Firstly, we'll look at the variables that might affect solubility, then we'll move on to look at how we can record results appropriately, and finally, we'll get into that investigation looking at solubility.

So, let's get started by looking at the variables that might affect the solubility of a solute.

Now, anyone who's ordered a drink at a cafe or a restaurant will be familiar with the idea that drinks are usually presented with a spoon of some sort, and that's to help us to add some sugar to it or perhaps to stir the drink up so that it helps these substances that may be added to our hot drink can dissolve.

Now, if you recall, dissolving is a process during which a substance's particles, so that's the solute's particles, are able to separate and then spread throughout the other substance, the solvent, and that results in a substance no longer being seen.

So, stirring then is one way in which we could increase the solubility of sugar, for instance, in water.

Now, solubility is a term that scientists use to describe how well a solute is able to dissolve in a solvent to create a solution.

There are other factors that might affect solubility.

For instance, you might choose a different solvent for dissolving a particular solute.

So, if we look at iodine as our possible solute, we could perhaps try to also dissolve this in water, and we can see that it's not dissolved very well.

But if we use a different solvent, for instance cyclohexane, we can see that the iodine is dissolved a lot better.

So, solubility of iodine is increased or improved by using the solvent of cyclohexane versus the solvent of water.

So, solubility can be affected by stirring, it can be affected by the choice of the solvent that that solute is being dissolved into, but there are other ways that solubility could be affected as well.

For instance, we could look at things like the size of the solute pieces, the size of that starting material that we're trying to add into our solvent.

We could look at how much or the mass of the solute that we're trying to dissolve.

We could also look at perhaps the temperature of the solvent that's being used when we're creating that solution.

Time for a quick check.

What is the correct term that's used to describe how well a substance dissolves? Take a moment and come back when you're ready to check your answer.

Well done if you chose solubility.

This is one of those examples where a lot of the terms that we're using within our topic of solutions can get a little bit tricky to keep track of, so it's always good to double check that you really understand the definitions of these familiarly sounding words.

So, well done if you chose solubility.

Let's move to the first task of today's lesson.

Izzy's not convinced that stirring actually affects solubility.

So, to test this, she has collected the equipment that's shown.

What you've been asked to do then is to write a method that Izzy can follow so she can find out how long it takes for a sugar cube to dissolve when it's stirred and when it's not stirred.

Within this method, you want to make sure that you are referring to the equipment that she's collected.

And don't forget that a method includes things like command words, short, sharp sentences that uses concise language.

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

Let's see how you got on.

Now, there's lots of different ways that you could have written out the method that Izzy could follow to find out whether or not stirring will impact the solubility of her sugar cubes.

The main thing that we wanted to do was to make sure that you have a logical order.

So, you can see here that all of our sentences are short and they've been numbered so we can keep track of what order they go into.

They also include these command words such as measure, pour, add, stir, record.

So, a lot of the sentences are starting with those command words.

And she's also referencing the equipment that Izzy has collected.

So, the main points we want to make sure we've included within the method is that you're measuring out a specific volume of water.

You also want to make sure that you're saying when to start that stopwatch and when to stop the stopwatch.

Ideally, you've also included the information to record the time and to repeat the investigation, but at this point, if you haven't remembered to put that in your method, that's okay.

A method can be a really tricky thing to write, and I would always recommend at the start to actually maybe sketch out how you would carry out the investigation and then use those sketches to write a sentence for that particular step that you've sketched out and then decide the order that you'd like to put it in.

So, it can take a little bit of time to write a method, and don't worry if you didn't get all these steps in, it will improve with more practise that you get, but very well done for having a go here.

Now that we're feeling a little more confident looking at the different variables that might affect the solubility of a solute, let's look at how we can keep track of how those variables change by how we record our results.

Whenever an experiment is being conducted, measurements or observations are constantly being made.

Now, what scientists do is they try to record those measurements and observations, specific ones, in a table of results.

And a table of results is simply an orderly way of recording that collected data.

Now, when we create a table of results, we do so in a very standardised way.

The first thing that we do is use a pencil, and that's because if you do make any mistakes as you're creating it, you can easily correct it.

The next piece of equipment you might need when you create this table of results is to use a ruler.

And what this helps to do is a few different things.

Firstly, it helps to create that order that a table of results is trying to provide, and it does that by clearly creating the columns for each of your variables and the rows that you're gonna create for each of your measurements.

Now, you'll notice in this basic table that's been drawn is that there's also lines around the outside.

And what that does is help to keep the data that you are recording in it very isolated and away from anything you would be drawing or writing around the outside so you can easily find the information going forward.

Now, some of the most important information you'll find in a table of results is actually in the headings.

These will include the labels for the independent and dependent variables.

That's because the independent variable is what's changing and the dependent variable is what is being measured or observed, and therefore most importantly needing recording throughout this investigation.

Control variables aren't normally recorded in a table of results because by their definition, they're not changing and therefore it should simply be listed in the method how it's being controlled.

Now, when you're writing your headings in, the independent variable tends to be what's written first, or on the left-hand side of your table, and the dependent variable tends to be written next, or on the right-hand side of your table.

And that's a really easy way of thinking about this is that what you are changing physically in your own investigation is what you need to do first, and then the measurement that depends on how that independent variable has changed is what comes next in your table.

Let's take a moment to see how you're getting on.

True or false, control variables are recorded in a table of results? Well done if you said false, but what's the reason why? Is it because control variables change during an investigation or is it because control variables do not change during an investigation? Well done if you said b, control variables do not change during investigation and therefore they don't normally need recording in a table of results.

Well done.

Now, we already know that the headings in our table of results will include the independent and dependent variables, but it also can include the units for that variable in which it's measured, and we can see that here in this table and that the mass is being measured in grammes, and then the spring extension is being measured in centimetres.

And those units then are indicated within brackets within that heading.

So, why put them in the headings? Well, what it does is it saves us a little bit of hassle.

It prevents us from repeatedly including those units when you're recording your measurements.

It means that you're keeping your table a little bit more organised, a little bit more clear so that all you'll be looking at is your measurements and your observations rather than having to continually muddle the table by including the units in every recording.

Now, sometimes you might see a table of results that's been written horizontally rather than vertically like I've shown earlier.

But what you will notice is that it still includes both the variables, the independent and dependent variable.

Now, interesting in this particular table, what's included is the range of values of how that independent variable is going to change throughout that experiment.

Now, it's shown here in the horizontal table, but it could also be written in our vertical table.

So, you're already deciding before starting that practical how you plan to change the independent variable as you go through.

At this point, our table is nearly complete.

What we need to do now then is to follow the method and record the results for the dependent variable as you go forward.

So, when you're recording the measurements in your table of results, it's really important that you're ensuring what you're recording is consistent.

And one of the easiest ways to do that is to ensure you have the same number of decimal places for all your measurements.

If we look at these two tables as examples here, we can see that the one on the left as you go down each column has the same number of decimal places.

For instance, in the mass there goes to the 100s, and in the spring extension it goes to the 10th decimal place.

If we look at the one on the right and we compare just the masses, we can see that one has a decimal place and does not.

And with the spring extension, again, one has a decimal place and one does not.

This inconsistency is going to create a bit of questioning by those looking at your table of results because it doesn't look like some of your results are as accurate as they could be.

Did you mean in the spring extension measurement 6.

0, 6.

1, 6.

2, and just chose for that particular measurement to round it, or was it actually 6 centimetres? So, it is always important that you're consistent in what you're recording.

Let's do another quick check before we continue.

Which two of the following should you do when you're creating or using a table of results? Pause the video here and come back when you're ready to check your answers.

Well done if you chose a, be consistent in how your measurements are recorded, and d, include the independent and dependent variables in your table.

For b, really you should be using a pencil to draw the lines, not a pen, so that you can easily fix any mistakes.

And for c, you don't include the units with every measurement, you should only put the units in the heading for your table.

Well done if you got a and d.

Now, you might be wondering why I'm banging on about the standardised way in which we create and then use a table of results.

Surely it should be much simpler than that.

Why do I need to put lines around the outside of my table? Why do I need to make sure that I am including the correct number of decimal places and et cetera? And the reason is because the data that you're actually recording in that table of results is gonna form the basis for the evidence that you're using to answer the question of that experiment.

And if you design that table of results as best you can, it's going to allow for a really quick and easy assessment of that collected measurements and observations, and it's gonna allow you to do a few things.

For instance, it will help you to identify if there's a pattern or a trend in some of the values.

So, are you recording results that are repeatable? Are you finding any values that don't fit that pattern or trend that you may have seen in the values you've collected? And if not, should you maybe take some more measurements? Would that help you to see if there's any trend developing in the values that you're recording? And if your table isn't well designed in the first place, it's gonna be really tricky to find those patterns and answer those questions.

So, why are we looking for a pattern in our values and why specifically would we be looking to see if there's any values that don't fit? And the reason is because any result that doesn't fit an observed trend is considered then an anomalous result or an anomaly, it doesn't quite fit the pattern.

And when we're talking about looking for patterns, we're not saying as the independent variable changes, we're saying are there any ones that look odd when you look at the repeats that you've carried out for a particular independent value? So, if we look at the 200 gramme mass that was used, and we read across from 11.

4 to 11.

3, and then suddenly we have this value of 13.

9, and that doesn't seem to fit the trend of what has been recorded previously, so that would be identified as an anomalous result.

If you look at the 400 gramme row mass, we can see again a possible anomalous result of 39.

6 here.

It doesn't quite fit the trend and therefore, hmm, it's an anomaly and I might need to do something about that.

The other thing a really well-designed table of results can be used to do is to record any mean calculations of the measurements that you've managed to record throughout your experiment.

Now, as a reminder, to find the mean of your values, you'll take the sum of your results and then divide that value by the number of the results you've added together.

So, if we look at this first set of results for 100 gramme mass, we'd add all of those results together, divide by 3, and we end up with a mean of 5.

7, which I could then take that calculation and put it into my table so we can see if there's any patterns within the means that develop.

Now, I said earlier about identifying anomalous results, and there's a really important reason why.

When you are calculating the mean value, you do not include an anomalous result.

Now, you could have chosen to perhaps repeat that measurement, so replaced it in some way, but if you haven't, what you'll do is actually cross those results out and not include them in your final mean calculation.

So, if I use the mean calculations for 200, I'm going to get a value of 11.

35, but because remember, I'm keeping the consistent recording, I'm going to have it to one decimal place, and that would make it 11.

4.

Let's try one more quick check.

Which term describes a result that does not fit an observed trend? Well done if you said anomalous.

Let's move on to the next task in today's lesson.

Spun sugar is a really common decoration for baked goods.

And when you're making a spun sugar decoration, you start by creating a sugar solution.

Sugar is the solute, and then water is the solvent.

Now Jun is preparing for a baking competition and he's trying to find out which sugar will dissolve the fastest, therefore having the greatest solubility in water, and he's going to investigate sugar cubes, granulated sugar, and powdered sugar.

What I'd like you to do for this task is to create a table of results that Jun could use to record how long it takes for 2 grammes of each type of sugar to dissolve in 100 centimetres cubed of water.

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

Okay, let's see how you got on.

Now, there were a few different ways you could have laid out your table of results, and this is just one of those examples.

But what I have done here, and that I hope that you've also put on here is looking at these headings to start with.

I've got the type of sugar is identified as my independent variable because that's what I'm gonna be changing within the practical, and that's why it's listed first.

So, the types of sugars, and then I've listed them as I'm changing cubes, the granulated, and the powdered sugar.

The other heading then is the dependent variable, what's being measured, and that's the time taken for it to dissolve.

And I've included the units of seconds within the brackets there.

I've also included multiple trials.

So, I won't just dissolve the sugar cube once, I'm going to do it three times and then I've left space for me to record a calculated mean time that it's taken for those to dissolve.

I've also ensured that I've used a ruler to create those straight lines so that any of the recordings of my measurements that I'm making aren't getting muddled up by scrappy lines around the side.

And that it also means that I can very easily compare results down a column and across a row.

So, lots of things to keep track of when you're trying to draw a table of results.

Hopefully what you've managed to do is at least put your independent and dependent variables in the headings, included your units, and had those different types of sugar added as the independent variable changes along the side.

Well done on a tricky task.

Now that we're feeling a bit more comfortable identifying variables that might affect solubility and how we might create a table in order to record results from a practical, let's move on to investigate solubility.

So, when we're creating a solution, a scientist can influence the conditions of either part of our solutions, the solute or the solvent.

So, those are things that we might think about changing in order to improve the solubility of a substance.

So, for instance, with the solute, we might change the mass that we're trying to dissolve or the size of the pieces of that solute we're trying to dissolve.

When we're looking at the solvent, we might look at the choice of the solvent that we're using, or we might also look at the temperature of that solvent.

So, in general, if you use a smaller mass of solute, it will have greater solubility, and that means essentially that it would dissolve faster.

So, if you are making a cup of tea, the less sugar that you might put in it, the faster it would dissolve.

And so, what we could say then is if it has a lower mass for solute, the greater its solubility.

Another way that I might be able to increase the solubility of my solute is to break it into smaller pieces.

If we stick with that example of making a cup of tea and adding sugar to it, you could add sugar cubes or you might use granulated sugar.

Maybe you've run out of both and instead you use powdered sugar.

All of these would work to sweeten your tea, but the smaller the pieces of that solute or the sugar in this case that you're adding, the greater the solubility, the faster it will dissolve.

And anybody who's used a sugar cube versus granulated sugar will notice that the granulated sugar dissolves that little bit faster.

We touched on this a little bit earlier in the lesson, but just as another reminder that solubility will increase if you choose a more appropriate solvent.

So, here we have sticking with our solute of sugar, if we were to use it in cyclohexane, we can see that it hasn't really dissolved that much.

But if we were to put that sugar into water because we now have a clear, colourless solution forming, we can say that the sugar has dissolved and therefore the water gives greater solubility if sugar is my solute.

Time for a quick check now.

Which of these apparatus would you be using to measure the mass of solute that might be used in an experiment? Well done if you chose b, that is our balance.

A represents a tripod and c represents the gauze.

Let's try another one.

Which apparatus is best to use to measure the volume of solvent used in an experiment? Well done if you chose c.

Now we can see that there are little volume markings on all of the apparatus that's listed here, but c is our measuring cylinder, and that's what we use specifically to measure out volume.

A represents a beaker, and B represents a conical flask.

But both of these are used for reactions to take place in, and the markings on the side are guides for how much volume they can hold, not used for measuring out a volume.

Okay, one more check.

Which set of conditions will have the greatest solubility? Pause the video here and come back when you're ready to check your answer.

Well done if you chose c.

Now, if we are looking at this just comparing each condition at a time, we can see that a is granulated sugar, but b and c both have powdered sugar.

And we know that the smaller the solute is, the faster it will dissolve or the greater solubility it will have, so my answers are now reduced to b or c.

When I compare the volume of water, that has stayed the same.

Now, b is not being stirred, but c is.

And because of that, c is the best answer, the best conditions in order to have the greatest solubility.

Well done for trying to compare quite a lot of information in one go.

Let's move on to the last task in today's lesson.

Jun has decided that he's going to use granulated sugar as his solute to create a sugar solution in his baking competition.

And he'd like your help in finding out what temperature of water he should use to make that solution.

You're going to carry out an investigation to decide in which temperature of 100 centimetres cubed water 2 grammes of granulated sugar is going to dissolve the fastest, and therefore have the greatest solubility.

You should aim to try at least three different temperatures of water, and you're gonna record your measurements in an appropriate table of results.

If you finish that then, you want to examine your results and decide if any of them are anomalous.

and if so, which ones are they? Now, the next slide will show you a possible method that you could follow, and you might want to pause the video there to use as reference as you carry out your investigation.

If you don't have access to the materials to do this investigation, you could instead watch the demonstration that follows and gather your results from that.

So, once you've gathered all of your equipment together, you will measure out 100 centimetres cubed of water using your measuring cylinder, pour it into the beaker, and then lower a thermometer that's being held by a clamp stand into that water.

We don't want the thermometer resting at the bottom of the beaker, it should be in the water.

And then, you're gonna need to leave the thermometer to settle to a constant temperature as best you can.

It will take time for the thermometer to react to the temperature of the solvent, and here we can see it as resting at roundabout 16 degrees.

Once you've got that and the temperature is recorded in your table of results, you're going to measure out your 2 grammes of solute.

So, this is gonna be your granulated sugar, and we're using a balance in order to do that.

Once you have that, you wanna make sure that you have your stirring rod at the ready and a stopwatch nearby.

Add the saute to the solvent and start that stopwatch immediately.

And that's because as soon as the solute hits the solvent, it will start to dissolve (beaker clinking) and we want to be making sure we're keeping track of every single moment that that's possibly happening.

(beaker clinking) The stirring rod there is, if you remember it, stirring does help to improve the solubility or how quickly and easily a solute is able to dissolve in our solvent, and we're going to stir that as we go along.

It can be a little tricky doing that around a thermometer that's held in place with a clamp stand.

Just do the best you can, we're trying to keep it as constant 'cause it's one of our control variables to stir this solution and the solute into that solvent.

(beaker clinking) Now, you're going to need to keep track of what's happening in there.

So, looking down at the top of your beaker, keeping track until your solution is clear, telling us that no more solute is visible and it is all dissolved.

At that point, you stop and record the time on your stopwatch.

At that point then, you're going to replace your beaker or clean it out at least three times and reuse it, add another 100 centimetres cubed and take the temperature of that warmed water.

Here is at 43 degrees.

Again, adding then your 2 grammes of solute and starting that stopwatch immediately so you can keep track of the full time it takes to dissolve and again, stirring so that we're being consistent between each one of our tests at the different temperatures and we're stirring completely and trying to be consistent in how we're stirring it, keeping track of when that solution has become clear, meaning there are no bits that can be seen and telling us that solute has completely dissolved.

(beaker clinking) Once that has happened, you're going to stop your stopwatch, record the time and again start again.

New beaker or cleaned beaker, 100 centimetres cubed of warmed water, taking the temperature of this.

And remember, it will take time to equalise, so give the thermometer time to respond to the temperature of your solvent.

Record that temperature in your table of results, add your 2 grammes of solute, (beaker clinking) start the stopwatch immediately when you do so, stirring that solution just as you have before, and then you'll stop that stopwatch when the solution has become clear and record that time.

Okay, let's see how you got on.

Now, your results might look very different from the ones that are listed here, but ideally, we were looking for you to record the results and the measurements from your investigation in an appropriate table.

So, what I'm looking for is that you have your first column is showing you the independent variable, which is the temperature of water, and the units should be in degrees centigrade.

You will have measured the temperature of that water before starting each trial and shown that temperature here and recorded it.

It doesn't necessarily need to be an exact 10, 20, 30 degrees centigrade.

It's a very tricky thing to control the temperature of water in an investigation.

So, as long as you recorded it and had three different temperatures, you are fine.

The dependent variable then of what you needed to record was the time taken to dissolve, and your units should measure what you recorded.

So, seconds is the standard unit that time is measured in, and that's what's been recorded here.

If you used the video, then trial one was shown, you might have used that as a guide then to do trials two and three.

And again, your measurements will be different slightly to the ones that are listed here.

These are just here as a guide and as an example.

We've included as well here a column for you to record the mean calculation of the different trials for those specific temperatures of water.

And so, we've added those trial measurements together, divided by the values, and then found our mean time taken to dissolve.

You'll notice here as well that an anomalous result has been identified, circled on the results table and disregarded when that mean value was calculated.

I hope you had a good time doing your investigation and that going through this table of results has helped you to understand how you can take what you've done in the lab to record for further analysis later on.

Well done on a great lesson today, guys.

Let's summarise what we've learned in today's lesson.

We've learned that the solubility of a substance describes how well it can dissolve in a particular solvent, and that solubility can be affected by several different variables, and that could include whether or not the solute that you've used to make that solution is stirred, the size of the solute pieces you start with, or even the mass of the solute you're trying to dissolve.

It could also be affected by the choice of the solvent that you're using or the temperature of the solvent you're using to make that solution.

We've also learned that when you're investigating solubility or any investigation, in fact, the measurements that are made will be recorded in a table of results, and that table of results will include the headings for the independent and dependent variables as well as the units that were used for those measurements.

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