Hello there, I'm Mr. Forbes and welcome to this lesson from the Energy of Moving Particles unit.

This lesson's called effective insulation and in it, we'll be carrying out an experiment to try and work out which materials make the best insulators.

By the end of this lesson, you're going to be able to carry out a fair test to investigate a range of insulators, working out which one is best.

That'll include carrying out a controlled experiment first.

Here are the keyword for the lesson, and the first is control experiments, and control experiments are done to find out a baseline set of data to which other experiments can be compared.

Independent variables are factors that can be changed during experiments to see how they affect dependent variables.

Dependent variables are measured during experiment to see how they're affected when you alter those independent variables.

And control variables are things that need to be kept constant to make sure the experiment is kept fair.

You can return to this slide at any point during the lesson.

The lesson's in three parts, and in the first part, we're gonna carry out a control experiment to find out what happens when you're cooling without any sort of insulation layer.

In the second part of the lesson, we're going to plan and carry out the investigation where we are going to use insulation to compare.

And in the third part, we're gonna look at those results and see which materials make the best insulators.

So, let's start by looking at our control experiment.

Energy can be conducted for one part of a substance to another by the process of particles vibrating, transferring their energy.

And thermal conductors are materials that transfer energy very quickly and most common example of that is a metal.

Metals are good thermal conductors and we use them to transfer energy quickly, perhaps when we're cooking food.

Thermal insulators transfer energy, but they do it very slowly, and so we use them to reduce energy transfer.

So, the handle of a kettle is made of plastic, because it doesn't transfer energy very quickly.

So, if you pick up the kettle, energy isn't transferred to your hand very quickly through that plastic.

In this lesson, we're gonna investigate how effective different materials are at keeping water hot, to see whether they're good thermal insulators or not.

And before we do that, we need to carry out an experiment that allows us to get a baseline set of data, a set of data we can compare the insulators to.

And that's a control experiment, an experiment designed to establish that baseline.

So, we can compare that to each of the insulators we test later in the lesson.

The control experiment is just going to be based upon using hot water and a glass beaker.

So, something like this.

We've got a glass beaker and we're gonna pour hot water into that beaker, perhaps boil it with a kettle and pour it in there.

We're then going to try and reduce some of the energy losses by other process, 'cause we're just looking at conduction.

So, we're gonna use a cardboard lid to reduce convection currents.

We'll need to measure the temperature of that liquid or that water.

So, what we're going to do is put a small hole in that cardboard lid and that's gonna allow a thermometer to be placed in it.

The water's gonna gradually cool towards room temperature as time goes on.

So, what we're going to do is basically start a timer and measure the temperature of that water as it cools, perhaps every 30 seconds or so.

We're going to need to select the thermometer.

So, what I'd like you to do is to select the correct type of thermometer for the experiment.

So, we've got a beaker of freshly boiled water is left to cool.

What's the most suitable range and resolution for the thermometer to measure it as it cools? So, pause the video, make a selection from the four thermometers there, and then restart please.

Welcome back.

Hopefully you selected the bottom one there.

That thermometer is gonna be measuring water.

It's gonna be cooling from just below 100 degrees Celsius and towards room temperature, which might get down to 20.

So, we need a range that covers both those values and that's thermometer D there.

We also want it to have a good resolution and the resolution available there is 1 degree Celsius, which is much better than the resolution of thermometer A.

So, well done if you selected D.

As we're concentrating on doing fair tests later, we need to make sure that the temperature of the water that we start with is the same every time.

And the easiest way to do that is to actually boil some water in a kettle, so it's up to 100 degrees, and then allow it to cool to a particular starting point when we've selected.

I'm gonna select the starting point of about 80 degrees Celsius.

Though you may select a different starting temperature, but 80 degrees is probably about as hot as you're going to be able to make the water at the starting experiment by the time you've set everything up, put the thermometer in place, and so on.

We're going to record the results of the cooling in a table and the table's gonna look something like this.

So, I've got all my times from zero second as the starting temperature, all the way up to 300 seconds, which is five minutes later.

And I'm recording the temperature every 30 seconds there.

So, I can already fill in the starting temperature, because I've decided on it.

It's 80.

0 degrees Celsius.

And then, I'm gonna record the temperatures as we go on in a table like this every 30 seconds.

What I'm actually interested in is the change in temperature over time.

So, I've added an extra row to my table here for change in temperature, and I'm gonna calculate the change in temperature for each of the times.

So, at the start of the experiment, I've got a change in temperature at zero, because obviously, it started at 80 degrees, and it's still 80 degrees.

The change in temperature for all the other times can be found by subtracting the initial temperature from the new temperature.

So, we can do that for 30 seconds.

And I find that the change in temperature there is minus 4 degrees Celsius.

And I can do that for the next at 60 seconds and I can find the change in temperature there is minus 8 degrees Celsius as well.

And so, I can continue with that process for each of the times.

And I get results, something like that.

The data for the experiment is going to be used to plot a cooling curve that's gonna show the decrease in temperature over time.

And I'm gonna have a graph of something like this.

Now, you can see this is a slightly unusual arrangement of the graph.

I've got the temperature change and the time on it, but they're in slightly different positions than you might be used to.

All of the values for the temperature are going to be, sorry, temperature change are going to be negative.

And so, I've drawn the x-axis at the top there.

So, here's the graph and what I'd like you to do is to see what conclusion can you make about the change in temperature over time based upon the graph shown? So, pause the video, make your selection from the three options, and restart please.

Welcome back.

Hopefully you notice that the change in temperature over time is decreasing.

It's cooling rapidly at first in the first few seconds, but then as you get a bit later on, it's decreasing.

It's not cooling as rapidly.

You can tell that, because the gradients' less steep towards the end of the graph there, towards the 300 seconds.

Well done if you've got that.

Okay, it's time for the first task and what I'd like you to do is to carry out the control experiment using the method below.

And you can see the instructions there.

You're gonna pour 100 centimetres cube of very hot water into the beaker, place the cardboard lid over the beaker, making sure that the thermometer bulb is in the water.

Then, you're gonna wait until the temperature falls to that starting temperature of 80 degrees Celsius.

Then, start the timer at that point.

And record the temperature every 30 seconds for five minutes.

You record the results at a table, something like this, and then calculate the change in temperature row for each of those different times.

So, pause the video, follow these instructions, and complete the results table, and restart when you're done.

Welcome back.

Hopefully you got results something like this.

Your results should show a gradual decrease in temperature and the rate of that decrease is becoming smaller over time.

So, we get big changes in temperature for the first 30 seconds, and smaller changes in temperature in the periods after that.

Well done if you've got that sort of pattern.

And now, we're going to plan and carry out the experiment where we're testing different insulators.

And later, we'll compare the results of these with that control experiment we've just completed.

So, to test the effectiveness of the insulators, what we're going to do is carry out basically the same experiment, but this time, we're gonna put an insulating layer around the beaker, around the outside to see how that affects the cooling.

So, we've got the hot water still containing that initial beaker with a lid and the thermometers just as before.

But this time, what we're going to do is place that beaker inside a slightly larger beaker, and that large beaker is gonna contain it and also going to contain a layer of different insulating materials that we're gonna put between the two.

So, the water in the inner beaker is now protected by that insulating layer, and hopefully that will reduce the rate of energy loss and reduce the rate of cooling.

During the experiment, what we do is we change one factor to find the effect on the other factor.

And there's two types of names we use for those types of factors.

We are changing the insulation used in each test and that's the independent variable.

The thing we change is the independent variable in the experiment.

And what we do is monitor its effect on the change in temperature, and that's the dependent variable in the experiment.

So, we have an independent variable that we change and a dependent variable that changes as a response to that.

Let's see if you understand that concept.

Which of the following should be changed during a scientific investigation? Is it the control variables, the dependent variables, or the independent variables? Pause the video and restart when you're done.

Welcome back.

Hopefully you selected independent variables.

We change those.

The dependent variables are things we monitor to see how they've responded and the control variables are things we should keep constant during the experiment.

So, these are the three types of variables.

Well done if you selected C.

To make the comparisons fair in this test, we can only change one thing, so we need to keep everything else controlled, the control variables.

We've already decided that we are going to start the experiment at a fixed starting temperature and that's one of the control variables.

The starting temperature of the water needs to be the same, and that's because hot water actually cools faster than warm water.

So, if we had different starting temperatures, that would affect the outcome.

The volume of the water also needs to be kept constant.

We need to use the same amount of water, because if we've got a larger volume of water, that might affect the results.

And the time allowed for cooling needs to be kept the same for each of the experiments for each of the tests.

So, there, three of the control variables.

The other control variable is actually the amount of insulation we used.

If we put a lot of insulation of one material around and only a little bit of insulation of a different material, that wouldn't be a fair test.

But amount is a fairly vague word.

We can't just say that.

We've gotta measure the amount in a particular way and make a decision on how we're measuring the amount.

So, there's a few different ways.

The first one is the thickness of the material.

We could actually measure different thicknesses and keep it the same.

So, we could use a ruler and maybe put a one centimetre thick layer of insulating material around the beaker, and that would be a fair test.

We're looking at thickness in that case.

Or we could have the total mass of the insulation, so we could measure the mass of that insulating material and you make sure there's the same amount of mass, let's say, 100 grammes of each insulating material is what we're allowed.

And that would make it a fair test as well.

So, we could either choose the thickness or the mass.

Okay, let's say if you understand fair testing.

Here's a set of results for two different materials, cotton wool and polystyrene beads.

And I'd like you to use the information provided to decide why you know that that test was unfair.

So, pause the video, decide why that was an unfair test, and then restart please.

Welcome back.

Hopefully you selected the option C there, different starting temperatures.

That's evident in a table that I've highlighted there.

You can see that they didn't start the experiment at the same temperature, and that would be unfair.

A, different insulators have been used in each test.

Well, that's the whole point of the experiment.

They are the things we need to change during it.

So, that doesn't make it an unfair test.

And we don't have information about B, different volumes of water.

There's no data in the table that tells us how much water's been used.

So, well done if you selected C.

Okay, now it's time for you to carry out the investigation and I've got all the instructions here.

So, I'd like you to read through those, and then I'd like you to follow the instructions to carry out the experiment.

You will record your results in a table like this one with a row in the table for each of the different materials that you test.

And hopefully you've got time to test about three different materials.

So, pause the video, follow the instructions to carry the experiment, and then restart when you're done please.

Okay, welcome back.

Hopefully you've got a set of data and that look something like this.

I've got three different materials and I've recorded the temperature as they cooled, all starting from my 80 degrees.

Though you may have used different materials, so obviously your results will look slightly different.

But well done if you've got patterns like this.

And now, we're onto the final part of the lesson.

What we're going to do is use our data to plot some graphs, and then look at those to see if we can compare insulators and decide which is the best insulating material.

So, let's do that.

So, hopefully you've got a set of data that shows you the cooling of different materials.

If not, I've got an example table here, and I'll use this data in my analysis.

And I've got quite a complete set.

I've got cotton wool, polystyrene beads, sand, and I've also included information for no insulation from our control experiment at the start, so that we can compare things to that.

Now, it's really easy when you've got complex tables of data to make simple mistakes.

So, I've got a pupil has made a mistake here when calculating a change in temperature for the testing cotton wool.

I'd like you to look carefully on that table and identify which value they've got wrong.

So, pause the video, try and identify it, and restart please.

Welcome back.

Hopefully you selected this here, 180 seconds.

As you can see, they've miscalculated the change in temperature.

They've got their mathematics wrong and the value should be minus 11.

5 degrees Celsius.

Well done if you've got that.

So, once I've got my data, I can plot that on a graph.

And what I'm gonna do is use a single set of axes.

I've got my time and temperature change axes there and I'm gonna draw a separate line for each of those sets of data.

So, I've calculated the change in temperature for each and I'm gonna draw one line for each material.

So, I'm gonna draw my line for polystyrene first, my first set of data, and I've got a smooth curve.

I plotted the point and join them with a single smooth curve, because it's not a straight line pattern.

I then repeat with my cotton wool and draw a separate line for that, labelling it in a key on the side.

And then, I can do sand, my third material.

And I mustn't forget to plot my control experiments.

So, this had no insulation and I've drawn that as well.

So, I've got four separate lines on the graph.

Now, to decide on which of the materials was the best insulator, I should know that the best insulator will have the smallest change in temperature.

It will allow the least energy to escape to the environment, so the water will be hot at the end.

So, the better insulator, the smaller the change in temperature.

So, if I've got a line like this, this one would be a good insulator compared to this material, which is a poor insulator.

The good insulator has had a temperature change of minus 10 degrees Celsius, so the temperature's not gone down by much, whereas the poor insulator has had a temperature change of minus 23.

So, it's nowhere near as good as an insulator.

Let's see if you can decide which material was the best thermal insulator based upon the outcome of the graph.

So, I've got all the data there plotted on the graph.

Which one of those four lines represents the best thermal insulator? Pause the video, make your decision, and restart please.

Welcome back.

Hopefully you selected C.

That's the best thermal insulator, because it's got the smallest temperature change.

Well done if you selected that.

One of the things that makes a good insulator is that the material has pockets of trapped air, air trapped inside it, which can't move around.

So, small pockets.

That's because air is a very poor thermal conductor, thermal energy does not pass through it very much at all.

So, it makes a great insulating material.

But unfortunately, the air can flow around.

So, I need to control the movement of the air as well.

So, I need to trap it in a small pocket in a bubble to stop that air moving around and transferring energy.

One good example of that is expanded polystyrene.

That's a plastic that has been processed, so that it contains very tiny pockets of trapped air, making it very light and containing billions of small bubbles.

So, that makes a very good thermal insulator, because it contains trapped air.

Let's see if you can decide on what makes something a good thermal insulator.

I've got a plastic bubble wrap here and I'd like to know why is that a good thermal insulator or very good thermal insulator.

So, you've got three options there.

So, pause the video, make a selection of which of those is correct or are correct, and then restart please.

Welcome back.

Hopefully you selected all of them.

And the reason bubble wrap is a very good thermal insulator is it's, well, it's made of plastic, so that's a good thermal insulator.

It contains air and that's a good thermal insulator as well.

And the air's trapped in small bubbles, so you can't have large convection currents forming, transferring energy from place to place either.

So, well done if you selected all three.

Okay, it's time for the final task of the lesson and this is you planning an investigation.

So, I'd like you to plan an investigation to find out how the thickness of an insulating layer affects the rate of cooling of an object that it's surround.

And your plan's got to include an equipment list, a diagram, descriptions of the variables, dependent, independent, and control, a step-by-step method, and the design of a suitable results table.

So, pause the video, write out your plan, and restart please.

And welcome back.

Your equipment list should include this sort of operator, a beaker to contain the water, thermometer to measure the temperature, some hot water, and that's what we're gonna allow to cool down.

Some sort of lid to prevent convection currents, because remember, we're looking at just insulation.

And then, materials that you're testing.

And we'll need to control the thickness of the layers.

So, we want something like layers of cloth, paper, felt, just one material, but we want to be able to make it into layers surrounding the object.

And then, perhaps a heat proof or heat resistant mat in the bottom there to prevent loss from the bottom.

My diagram shows how that's set up.

I've got my thermometer through a lid into a beak of water, and then I've got layers of material around.

And in my diagram, I've drawn two layers.

I'm using felt as my material and it's important that I show that, because I'll be changing the number of layers of the material to control the thickness.

And here's the description of the variables.

The independent variable is the number of layers of the insulating material, all the thickness, if we're measuring the thickness directly.

The dependent variable is going to be the change in temperature over time.

And the control variables.

The things we need to keep the same are the starting temperature, the volume of water we use, and the time the water is allowed to go for.

Well done if you've got all these.

And finally, here's a suitable method and you can read through that, and it shows the same sort of process we used earlier, but this time, we're just varying the thickness or number of layers of insulating material instead of changing the material itself.

And I've got a results table that shows some things similar, but this time, I'm just looking at the start and end temperatures.

I really don't need the information about the cooling in between, 'cause I just want a comparison between the number of layers and the change in temperature.

So, well done if you've got something like this.

Okay, we've reached the end.

Okay, we're nearly at the end, so let's have a quick summary.

So, the effectiveness.

Okay, we're nearly at the end, so a quick summary.

The effectiveness of thermal insulators can be tested by measuring the cooling of a hot, insulated container.

And we've used hot water for that.

We can carry out a control experiment to get a baseline set of results, so we can make a comparison.

And in an investigation of cooling, the independent variable is the type of insulator.

And that's the thing we changed.

The dependent variable was the change in temperature.

And the control variables included starting temperature, volume of water, and the mass of the insulator, the amount of insulator we use there.

We also found out that small pockets of trapped air are commonly found in good thermal insulators.

Well done for reaching the end of the lesson.

I'll see you in the next one.