Welcome to today's lesson, Cooling Curve: Practical.

It's part of the unit Fuels and Energetics.

My name is Ms. Mytum-Smithson.

I'm so pleased that you've come along to learn with me today.

Today's lesson is an investigation.

We're going to gather data and create a cooling curve, then identify on a graph where state changes occur.

Don't worry if you haven't drawn very many graphs in science yet.

We're going to work through this together step by step, and by the end of the lesson you'll be feeling much more confident about handling data.

Today's keywords are temperature, plateau, freezing, melting point.

On the next slide, there's some sentences that include these keywords, so if you want to read them, then pause the video and press play when you're ready to start the lesson.

Today's lesson consists of two learning cycles.

Firstly, we're going to start and look at investigating temperature.

Then we're going to look at how we can draw our cooling curve and what it means.

So first of all, let's start with our first learning cycle, investigating temperature.

Let's get learning.

Substances are not fixed in one physical state forever.

A substance in the liquid state at room temperature, for example, water, can be cooled and changed into the solid state.

This would then become ice.

So changing a substance's state requires an energy transfer either from the surroundings to the substance or from the substance to the surroundings.

So here's our images here.

We've got heating and cooling.

So here you can see that heating is where energy from the surroundings is taken into the substance, and cooling is where energy from the substance goes into the surroundings.

When a substance is heated, energy is transferred from the surroundings to the substance.

You probably used a heating up water in a beaker with a Bunsen burner.

The transfer can be measured using a thermometer to read the temperature change, and this is measured in degrees Celsius.

Its symbol is a little circle, like a degree sign that you would use in maths, and a capital C.

Here I've got a beaker, and in the beaker is some water and a thermometer to measure the temperature of that water.

We're going to heat it up.

As the particles gain more energy when they're heated, they move around faster.

You can see here they're moving around faster.

Eventually the substance will gain enough energy that the particles will overcome those forces holding them together, and then they're going to be able to change state.

So in this example, we're looking at the change of state being from a liquid state to a gas state.

Now whilst that state change is happening, the temperature no longer changes even though the water is still being heated.

So we wouldn't see any temperature change, even though that water's being heated.

A quick check for understanding now.

True or false, as a substance in the solid state cools, it will eventually melt.

Is that true or is that false? Pause the video for some thinking time and then press play when you've got your answer.

Well done if you said that that statement was false.

Now you've got two justifications.

A substance in the solid state must be cool to melt it.

A substance in the solid state must be heated to melt it.

Pause the video for some thinking time.

Press play when you've got your answer.

Well done if you said B, a substance in the solid state must be heated to melt it.

Well done.

As a substance in the gas state cools, it will eventually condense.

Is that statement true or is that false? Pause the video for some thinking time and press play when you've got your answer.

Well done if you said that that was true.

As a substance in the gas state cools, it will eventually condense.

What's the justification for this? As they cool, the particles have more energy and are able to overcome forces of attraction between them, or is it, as they cool, the particles have less energy and are no longer able to overcome forces of attraction between them? Pause the video and have a little think.

Press play when you've got your answer.

Well done if you said B, as they cool, the particles have got less energy and are no longer able to overcome the forces of attraction between them.

So well done if you got that one right.

Here's a graph showing what happens when you heat up a substance.

So as time goes on, we measure the temperature, and the temperature of the substance can be plotted as it changes.

And here we are looking at temperature increase.

The changes of state are represented as a plateau, so that's a horizontal line.

So this is a heating curve, and on a heating curve, these plateaus represent melting and boiling.

As you can see, initially, the substance would be a solid and over time, you can see that you would heat it up, and at some point, you would get this plateau, and that plateau represents melting.

You would continue heating that, and then you'll get another plateau where the temperature wouldn't increase anymore, and that would represent boiling.

You could also carry out an experiment the same, but this time taking a gas and cooling it over time and plotting the points on a graph.

So here you can see that the plateaus here are condensing and freezing.

As that gas cools down, you'll see it initially condenses, and then once it's in a liquid state, if you kept on cooling it, it would eventually freeze and becoming a solid state.

So you can see those two plateaus representing condensing and freezing.

When a substance cools down, the particles transfer some of their energy to the surroundings, and this means that the particles slow down.

As the substance cools down, the temperature will remain constant at that state change.

So from a gas to a liquid, at that point the substance is cooling down, and the temperature will remain the same.

Eventually, the particles will no longer have enough energy to overcome the forces of attraction, and so they will change state.

Substances in the gas state will condense at their condensing point.

Remember, that's the same temperature as their boiling point.

And substances in the liquid state will freeze at their freezing point.

And remember, that is the same temperature as their melting point.

Here's a quick check for understanding.

Which part of the graph is a plateau? Pause the video, have a think, choose your answer, and then press play, and I'll tell you if you're right or not.

Well done if you said A.

A is the plateau.

That's that horizontal line.

Which part of the graph shows a state change? Pause the video now, have a little think, choose your answer, and then press play, and we'll go through the answer together.

Well done if you said it's A.

That is a plateau and that represents a state change.

Well done if you got that one right.

Which part of the graph shows melting? Pause the video, select your answer, and then press play, and we'll go through it together.

Well done if you said it was C.

Remember, a horizontal line, a plateau in the graph, shows a change of state.

So that part of the graph C, shows that it's melting.

Well done if you got that one correct.

Which part of the graph shows boiling? Pause the video now, have a think, and then press play when you've got your answer.

Well done if you said that that is B.

Remember, a plateau or a horizontal line represents a change of state, so that is showing boiling.

Well done if you got that one correct.

Here's part one of task A.

Identifying correct the four mistakes in the following information.

So you've got a graph that says boiling, condensing, temperature and time on it.

A state change can be identified on a graph of thermometer versus time when the temperature remains constant for a period of time.

We call this flattening.

So identify the four mistakes and correct them, and then press play when you've completed your task.

Well done if you managed to identify and correct the four mistakes.

So the two plateaus, the first one is melting, the second one's boiling, and it should have been a graph of temperature versus time, not thermometer versus time.

And we call this a plateau.

Remember, a plateau is a horizontal line that represents a change of state in this graph.

Well done if you got all of those four correct.

Alex has provided you with an unknown chemical and heated it up.

He wants you to observe what happens after you remove it from the heat and place it in the ice bath.

Make a prediction about what will happen when you remove the sample from the heated water bath.

Record your observation, so that's what you see, of how your sample appears after you remove it from the heated water bath.

Follow the method provided on the next slide to complete this investigation.

Record your observations of how your sample appears at the end of the investigation.

Here's the equipment that you will be given, and here's how you need to set it up.

So you've got to clamp and stand.

You're going to be able to clamp the thermometer in the boiling tube with your sample in it, and that's gonna be placed in an ice bath.

It might be a beaker or it might be a tub that your teacher has given you.

So the first thing you're going to do is you're going to collect the sample from your teacher.

Make a note of what the sample looks like before you start the experiment.

Place the boiling tube containing the sample into the ice bath.

Place your thermometer in it, and make sure it's suspended in it so that it's not right at the top and it's not right at the bottom.

Record the temperature every 30 seconds and make a note of what the sample looks like after a few minutes.

You need to make sure that you're familiar with these instructions before you attempt the practical.

Well done for completing that practical.

So your prediction about what will happen when you remove the sample from the heated water bath.

So it might look like this.

After the sample is removed from the heat, it will cool down and the temperature will decrease.

It might change from liquid to solid.

That's freezing.

Observe the appearance of your sample after you remove it from the heated water bath.

So at the beginning of the experiment, the substance is colourless and in the liquid state.

Let's have a look at my results.

So here's my results.

Yours might look similar to this.

So the time, we measured the temperature at the start, and then every 30 seconds.

So it started at 42 and it cooled down, and eventually got to 20, which was the room temperature that I was working in.

And observed the appearance of your sample at the end of the investigation.

So at the end of the experiment, the substance is white and in the solid state.

Well done if you got results similar to mine.

We've now completed the first learning cycle, investigating temperature.

Now we're going to look at drawing cooling curves.

So heating and cooling curves plots the temperature against time.

So you can see on the x-axis, the horizontal axis, we've got time in seconds, and on the y-axis, the vertical axis, we've got temperature in degrees C.

And you can see there we've got little crosses representing our data.

Plotting the data on a graph is just like using X-Y coordinates in maths.

So I want you to draw a cross where these two coordinates meet.

So if you have a look here, you can see we've got time at 30, and then we've got temperature at 16.

All we're going to do is plot a little cross there, and then we're going to join up those crosses together to draw our heating curve.

Let's watch that data be plotted again.

You can see the line of best fit that's being drawn at this point.

Now we've got a change of state coming up that we know is a plateau.

So that's a change of state from a solid to a liquid state.

True or false, when drawing a heating curve, time is plotted on the y-axis.

Is that true or is that false? Then what I want you to do is justify your answer.

So you've got two choices of statements.

Temperature is plotted on the x-axis, so that's a horizontal one with time plotted on the y-axis.

So the y-axis is the vertical axis.

The up and down one.

So time is plotted on the x-axis, the horizontal one, with temperature plotted on the y-axis.

Choose your answers.

So pause the video once you do that, and then press play and we'll go through it together.

Well done if you said that that was false.

Remember, time is plotted on the x-axis, with temperature plotted on the y-axis.

So well done if you got that one correct.

We've got some data here.

And what I'd like you to do is identify the mistake Laura has made with plotting this data.

So pause the video, think about what mistake Laura's made, and then press play, and we'll go through the answer.

So well done if you spotted that Laura had plotted the points for the temperature instead of time.

So she'd mixed up the y-axis and the x-axis together, and that's why her data looks like that.

She doesn't have a horizontal plateau.

So she doesn't have a plateau.

She's got this vertical line instead.

If you actually plotted that data, here's what it would look like.

So you can see there that you've got two plateaus.

So well done if you've got that correct.

Here's task B.

Alex completed another investigation and has collected some data.

What I'd like you to do is plot the points on a graph, label the graph with the following four labels.

So I want you to put on the melting point, the freezing point, solid state, liquid state.

I want you then to describe the arrangement and movement of particles in the solid and liquid state.

So pause the video while you complete that, and press play and we'll go through the answers.

Well done for completing that.

Hopefully you've got a graph that looks very similar to this one.

So I wanted you to label the graph with the following four labels.

So the melting point and the freezing point are actually the same point, so that here's where the melting and freezing takes place.

So this is the plateau.

Remember, the horizontal part of the graph representing a change of state.

So that's a melting and freezing point.

Then the solid state.

So below the freezing point.

It's going to be in the solid state.

And above that it's going to be in the liquid state.

So you should have a graph that looks similar to this one.

Well done if you got that correct.

Now we're going to look at how the particles move and are arranged in a solid state and a liquid state.

So in the liquid state, remember, particles are randomly arranged and they're free to slide and move past their neighbours.

In the solid state, remember, particles are in a fixed position and can only vibrate.

Particles are regularly arranged.

Here's a summary for today's lesson.

As a substance cools, it transfers energy into the surroundings by heating it up.

If it cools down enough, it can change state.

Substances in the gas state will condense as they cool past their boiling point, and liquid state will freeze as they cool past their melting point.

Energy is released to the surroundings as substance cools, and this is observed as a decrease in temperature.

Graphs provide a visual representation of data for easy analysis.

State changes are visible as plateaus on heating and cooling curves.

Well done for working really hard this lesson.

I hope you're now more confident in plotting graphs about heating curves and cooling curves and being able to interpret them.

I hope to see you again sometime soon.