Welcome to today's lesson on heating and cooling, it's part of the fuels and energetics topic.

My name's Mrs. Might-Smithson.

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

We're going to focus on two keywords during this lesson, exothermic and endothermic.

By the end of the lesson, you should feel much more confident about explaining why some changes of state are exothermic and some are endothermic.

The next slide has got some sentences that use these keywords.

If you wish to read them, pause the next slide, and then press play when you're ready to learn.

Today's lesson consists of three learning cycles, heating and cooling, endothermic and exothermic, and energy transfers.

The first learning cycle that we're going to do is heating and cooling, so let's get going.

When a substance is heated, the temperature of that substance increases.

If you take a look at the picture of the kettle, you can see some water in it.

That water in the kettle has been heated, and it's now at a higher temperature.

So it's gone from being at 25 degrees C to 100 degrees C, that's the boiling temperature of water.

When a substance cools, the temperature of that substance decreases.

So if we have a look at this fizzy drink, the fizzy drink has cooled in a fridge and it's now at a lower temperature.

So it's now gone from 25 degrees C, which is approximately room temperature, to four degrees C, which is much cooler.

A quick check for understanding now, which of these images have got objects that have been heated? A cooked pizza, water in the snowball, hot water bottle.

There might be more than one correct answer.

A hot water bottle, if you're not familiar with it, is a rubber bottle that has hot water placed in it to keep you warm.

Pause the video now for some thinking time, and press play when you've got your answers.

Well done if you said a cooked pizza and a hot water bottle, well done.

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

So the surroundings are just the air around it, or whatever it is around the object.

So if we have a look here, we've got a substance here.

And energy from the surroundings is going into that substance, and that's heating it up.

The opposite happens when cooling.

So when a substance cools, the energy is transferred from the substance to the surroundings.

So that's what happens when a substance is cooled.

Here we've got another example, so you might have done this in your lessons so far.

We've got some water that's been heated up on a bunsen burner, and the energy is being transferred from that hot flame, so that's the surroundings of the water, to the water.

So that's energy being transferred into that water, and that water is then heating up.

Here's an example that you're probably familiar with.

Here's a cup of tea, it's hot, and the energy from the hot cup of tea is being transferred to the cooler surrounding areas.

So here, you can see all the energy is being transferred to the surrounding areas which are cooler.

A quick check for understanding.

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

Energy is transferred from an object to the surroundings, or there is no transfer of energy.

Pause the video now for some thinking time, and press play when you're ready for the answer.

Well done if you said, A, energy is transferred from the surroundings to the substance.

That's what happens when the substance is heated up.

Three students are discussing cooling, who do you think has got the best description of cooling? Who do you agree with? Izzy says it's a bit like heating, energy moves from the surroundings to whatever is being cooled.

Sam says it is like the opposite of heating.

The energy moves from the hot tea to the air when a cup of tea is cooling.

Laura says, energy always stays in one place and it cannot move.

Pause the video now for some thinking time.

Write down who you agree with the most, and then press play when you're ready for the answer.

Well done if you said Sam.

Sam says it is like the opposite of heating.

So the energy moves from the hot tea to the air when a cup of tea is cooling.

You're absolutely correct, Sam is right.

What I'd like you to do for task A is draw two lines from heating and two lines from cooling to match up the descriptions.

On the left hand side, we've got the two words heating and cooling, and on the right hand side, we've got some descriptions.

Here are the descriptions.

Draw two lines from heating, two lines from cooling to match up those descriptions, here are the descriptions.

Temperature of substance increases.

Temperature of substance decreases.

Energy transferred to substance from surroundings.

Energy transferred from substance to surroundings.

Make sure you read them carefully, pause the video, complete the task, then press play when you've got the answers.

So, well done if you said that heating was to do with the temperature of the substance increasing, and the energy transferred to the substance from the surroundings.

And cooling is just the opposite, so that's the temperature of the substance decreases.

So it'll get cooler, and that energy transferred from the substance to the surroundings.

Well done if you've got all of those correct, you've done really well.

We've now completed our first learning cycle of heating and cooling.

Now, we're going to look at those two keywords for today's lesson, endothermic and exothermic.

After that, we're going to have a look at energy transfers in more detail.

Heating transfers energy from the surroundings into a substance.

So the substance heats up, it may melt, evaporate, or boil, and this is an endothermic process.

You might not have come across this word before, but if we break it down, we can look at how this word's made up of smaller words.

So here's the word endothermic.

Endo means into, and thermic means caused by heat.

So here, the energy from the surroundings goes into the drink.

And that thermal energy, so the heat, the thermal energy is transferred into the substance.

So if we have a look there, so the heat is transferred into the substance.

In this case, after a while, what will happen is those ice cubes will melt.

When substances cool, energy is transferred out of the substance into the surroundings.

This means that the substance cools down.

So if we have a look at our cup of tea, it's going to cool down.

It might condense or freeze, and this is an exothermic process.

So, again, that's quite a long word, but we'll break it down into two parts.

Exothermic means out of, and thermic, or anything that's thermal is caused by heat.

So here's the energy being transferred to the surroundings out of the cup of tea.

And that heat, that thermal energy is transferred out of the substance.

So we can see exothermic, that's where the heat is transferred out of the substance, it's a cooling down process.

Here's a table that summarises the differences between endothermic and exothermic.

So, first of all, we're going to have a look at endothermic.

Here, the energy is transferred from the surroundings into the substance, and the object temperature will increase and the surrounding temperature will decrease.

If we then take a look at exothermic, it's just the opposite.

So this time for exothermic, the energy is transferred from the substance to the surroundings.

That's gonna cause the temperature change of the object to decrease, and that means the temperature change of the surroundings is going to increase.

So if you just take a look there, you can see the differences between endothermic and exothermic processes.

Let's have a quick check for understanding.

Energy is transferred from a hot meal, this process is called.

Is it called exothermic, because energy is transferred from the food to the surrounding air? Is it exothermic because energy is transferred from the surrounding air to the food? Is it called endothermic because energy is transferred from the food to the surrounding air? Or is it because endothermic, because energy is transferred from the surrounding air to the food? Read these sentences really carefully.

I'm going to give you some thinking time.

So pause the video, and then press play when you've got your answer.

Well done if you said that it is exothermic because energy is transferred from the food to the surrounding air.

Remember, exome means out of, so it's transferred out of the food to the surrounding air.

Well done if you got that right.

Here's task B, what I want you to do for this is complete the diagram to show endothermic and exothermic processes.

So the surroundings are 20 degrees C, and we've got one beaker there that's got some water in and some ice cubes in, and it's measuring three degrees C.

And the other one is warmer water, which is 85 degrees C, as you can see by the reading on the thermometer.

For each beaker of water, I want you to label up some arrows to show where the energy transfers take place.

So, where does the energy take place? And where does it move to? I want you to add labels showing cooling, heating, endothermic, exothermic.

So those are the labels I want you to add to those diagrams. I want you to pause the video, complete the task, and press play when you're ready to go through the answers.

So here's our diagrams. You can see that the energy is transferred from the surroundings for the first one.

So you need to make sure your arrows are pointing into the substance, so into the water.

And the other one, it is energy being transferred to the surroundings.

Because the surroundings are cooler than the hot water, the energy will go from where it's hotter to where it's cooler.

Well done if you've got those arrows facing the right way.

This means that on the left hand side, you've got heating because that water is being heated up.

On the right hand side, that is going to cool down.

So it will no longer stay at 85 degrees C, eventually it'll just cool down to room temperature.

Which means that on the left hand side, we've got endothermic, remember, taking energy in.

And we've got exothermic on the right hand side, showing that energy is leaving that substance.

Well done if you got that right.

Now, we've had a look at heating and cooling, endothermic and exothermic, we're going to move on to our last learning cycle of energy transfers.

We're going to have a look at experiment now.

So a substance in the solid state is placed into a beaker with a thermometer.

The beaker's heated, and the temperature is measured every 10 seconds.

So if you have a look there, we've got a beaker, it's filled with this substance, which is a blue colour.

We've got the thermometer, and we're heating it from underneath using maybe something like a bunsen burner.

We can then draw a graph, on this graph, the results can be plotted, and this is called a heating curve.

So we've got time along the X axis.

This time, it's measured in seconds.

And we've got temperature, which is measured in degrees C, on the Y axis.

Here's a graph that shows what's happening when you heat up a substance.

So initially, as time goes on, what happens here is the temperature of the substance increases as the energy is being transferred to the substance.

So the particles remain in a fixed position, in a solid state, and the vibrations just increase.

If you continue heating, you will see, at some point, the temperature stops increasing and the substance starts to melt.

The energy at this point is used to overcome the forces of attraction, and that's why the temperature does not increase.

You can see here, that is when it's melting.

So that flat part is when it's melting.

So time's going on, but the temperature isn't increasing.

The point at which this starts to happen is the melting point.

And we can see in this, you can see here, as the temperature increases, the particles vibrate more, but they're still in a fixed position.

Once they can move past each other and change to the liquid state, that means that they've melted.

Once all the substance is in the liquid state, the temperature will stop increasing.

This means that the substance is boiling, and this is because the energy is used to overcome the forces of attraction until all the substance is in the gas state.

At this point, you can see we've got this flat part of the graph where time is moving on, but the temperature is not increasing.

You can see the point that this starts, that is the boiling point.

And then the substance will all be in the gas state, and that will mean that the temperature will start to increase again.

A quick check for understanding now.

What part of the graph shows that the substance is melting? Is it A, is it B, is it C, or is it D? So what part of the graph shows that the substance is melting? Pause the video now for some thinking time, press play when you've got your answer.

Well done if you said B, B is absolutely correct.

That is where the substance is being heated, but the temperature does not increase.

So what part of the graph is the substance in the gas state? Is it A, B, C, or D? So what part of the graph is the substance in the gas state? So you'll need to think back, and think back what each part of the graph means.

So whilst you're thinking, pause the video now, and then press play when you've got your answer.

Well done if you said D.

D is where all the substance is boiled, and therefore, it's in the gas state.

Well done if you got that correct.

Which part of the graph shows us the substance is boiling? Is it A, B, C, or D? Pause the video now for some thinking time, and press play when you're ready for the answer.

Well done if you said that C was the correct answer.

So that flat part of the graph, that's the second flat part of the graph.

So that means that the substance is boiling, and all that energy is being used to overcome those forces of attraction holding the liquid particles together.

Well done if you got that right.

Getting a little bit trickier now.

What parts or part of the graph shows the forces of attraction between the particles being overcome? Is it B only? Is it B and C? Is it A only? Or is it A and D? Pause the video for some thinking time, and press play when you're ready for the answer.

How did you get on? Well done if you said B and C.

Those flat part of the graph, that means that all the forces of attraction are being overcome.

So, well done if you got that right.

We're now going to look at our results from our experiment that we carried out earlier.

What we did here was every 10 seconds, we heated up a solid state substance.

What we did was we took the temperature of that substance every 10 seconds, so we've then plotted time along the X axis and temperature on the Y axis.

What we need to do now is draw a line of best fit, so we're gonna draw that through the majority of points.

Here it is, then we're going to label up the solid state, the liquid state, and the gas state, where they are.

There we go, and now we're going to have a look at where it's melting and where it's boiling.

Then we can look at the point at which it starts to change from being a upward slope to being a flat point, and that is gonna be the melting point.

And the same we can do for the boiling point.

What we can do now is we can draw a line using this graph and we can find out, by going through the Y axis, what the melting point temperature is, and what the boiling point temperature is.

So the melting point temperature is halfway between 40 and 50, and that's 45.

You can see that we've just drawn a line, we've just continued that flat line back through the Y axis, and we can do the same for the boiling point.

Using a ruler, draw a line all the way back through the Y axis, and we can see that that temperature is between 70 and 80.

So that boiling point temperature is 75 degrees C.

Scientists can carry out a similar experiment than the one that we've done, but this time, starting with a substance in the gas state and cooling it down.

They can measure the temperature at regular time intervals, and it will give you a cooling curve.

You can then see that the parts look very, very similar to the heating curve, just the opposite way around.

So we can then label up the gas state, the liquid state, and the solid state.

And those flat parts there are condensing and freezing.

That will give us our condensing point there, and the freezing point.

Remember, the condensing point is the same as the boiling point, and the freezing point is the same as the melting point.

True or false? This graph represents cooling data.

Have a little think.

Have you got your answer? I hope so.

So this represents cooling data, that's absolutely true.

And I want you to justify your answer, so you might need some thinking time for this.

As the time increases, the temperature increases.

As the time increases, the temperature decreases.

So pause the video now, press play when you're ready for the answer.

Well done if you thought that it was B.

As the time increases, the temperature decreases.

What I want you to do now is think about different parts of this graph.

So which part of the graph shows the gas condensing? Is it part A? Is it part B? Is it part C? Or is it part D? Pause the video now for thinking time, press play when you're ready for the answer.

Well done if you said part B, that part of the graph shows the gas condensing.

Well done if you got that right.

Which part or parts of the graph show that the temperature is staying the same? Is it A and D? Is it B and C? Is it only A? Or is it only B? Pause the video now to have a little think, and press play when you're ready for the answer.

Well done if you said B and C, those flat part of the graph show that the time is moving on, but the temperature stays the same.

Well done if you got that one right.

The freezing point of candle wax is 65 degrees C.

Which graph shows the correct information? Is it graph A, graph B, or graph C? Pause the video now for some thinking time, and press play when you've got an answer.

Well done if you said B, that's absolutely right.

It's the second part.

So it's a part between the solid state and the liquid state.

That flat part shows the correct freezing point of candle wax.

Well done if you got that right.

Well done for working so hard.

This is the last task of today's lesson.

I want you to admitting labels to the cooling curve.

You will not need to use all of them.

So here are the labels, boiling, condensing, freezing, melting, time, temperature, degrees C, solid state, liquid state, gas state.

Then I want you to add labels to the axis, showing the condensing point of 225 degrees C and the freezing point of 120 degrees C.

Pause the video now, complete the task, and press play when you're ready for the answer.

Well done for working hard and completing that task, here's your answers.

Temperature in degrees C going up the Y axis.

Then we've got gas state and solid state there.

And remember the horizontal ones for this, 'cause it's a cooling curve.

Got one that says freezing, and the other one which should be condensing.

That will then mean that this line here is the 120 degrees C freezing point, and 225 degrees condensing point.

Well done if you've got all those correct.

So part three to task C now, choose the correct labels to add to the curve.

You will not need to include all of these labels.

So here's your curve that you're going to label up.

You're going to give it a title, and that's either going to be heating curve or cooling curve.

You're going to label the axes, time and temperature.

You're going to then label up gas state, liquid state, solid state.

You've then got to label up boiling, condensing, freezing, melting, boiling point, condensing point, freezing point, melting point.

The substance melts at 50 degrees C and boils at 110 degrees C, add these labels to the axes of your curve.

What I want you to do now is pause the video, press play when you're ready for the answer.

Well done for the completing the task.

If you give this one a title of our heating curve, well done.

You then need to label temperature on the Y axis and time along the X axis.

Then you're going to label up solid state, liquid state, gas state.

Then we've got those flat bits to label up, melting and boiling.

And finally, we're going to label up melting point and boiling point.

And now, we've just got to label up the temperature.

So, 50 degrees C is that it melts at, and 110 is what it boils at.

So, well done if you've got all of those correct, that was a really difficult task.

Well done for working really hard this lesson.

This is task C, part four, it's going to describe a heating curve.

Complete the gaps with the words increases, decreases, stays the same, attraction, or repulsion.

You may use the words more than once, Initially, the temperature of the substance, until it starts to melt.

Then energy is needed to overcome the forces of.

This means that the temperature of the substance.

Once all the substance is in the liquid state, the temperature of the substance, until the substance starts to boil.

Energy is then needed to overcome the forces of, between particles so the temperature.

Once all the substance is in the gas state, the temperature.

Pause the video, complete the task, and then press play when you're ready for the answers.

Here are your answers for part four of task C.

Initially, the temperature of the substance increases until it starts to melt.

Then energy is needed to overcome the forces of attraction.

This means that the temperature of the substance stays the same.

Once all the substance is in the liquid state, the temperature of the substance increases until the substance starts to boil.

Energy is then needed to overcome the forces of attraction between particles, so the temperature stays the same.

Once all the substance is in the gas state, the temperature increases.

Well done if you got all that correct, that task was really difficult.

Here's today's summary about heating and cooling.

Heating transfers energy into a substance and can cause it to melt, evaporate, or boil.

Melting, evaporation, and boiling are endothermic.

As it cools, a substance transfers energy into the surroundings by heating, and it may condense or freeze.

Condensing and freezing are exothermic.

Well done for working hard this lesson.

Hopefully you're now more confident about using the keywords endothermic and exothermic, and you're also happy about describing heating and cooling curves.

I hope to see you again sometime soon.