Hello there, I'm Mr. Forbes, and welcome to this lesson from the heating and cooling unit.

The lesson is called energy and substance.

And in it, we're gonna be looking at the energy stored in different types of substance.

By the end of this lesson, you're going to be able to describe the differences between the energy of different substances when they're at the same temperature, and compare how difficult it is to heat different substances.

Here are the keywords that will help you through the lesson.

First of them is heating, and that's when energy transfers from a higher to a lower temperature substance.

So if you place a hot object near a cold object, the colder object will gain energy from the hotter one.

Next is specific heat capacity, and that's a property of a material, and that tells you how much energy is required to heat that material to increase its temperature.

And, finally, a thermal store, and that's the energy a substance has because of the random motion of its particles.

And that's related to its temperature.

This lesson's in two parts, and in the first part, we're gonna discuss how we can heat different substances and how their temperature change will be different depending on what type of substance they are.

And we'll carry up an experiment to measure how much energy is required to heat different substances.

In the second part of the lesson, we'll compare the thermal stores in different types of substance to see which one's greater, which one's lesser, and what effect that has on their ability to heat their surroundings.

So let's start by heating some different substances.

Imagine you're trying to heat two blocks of metal in an oven.

And I've got two blocks here, copper and aluminium, and I'm gonna place them both in an oven for five minutes to heat them up.

And what you might expect is that both blocks would end up at the same temperature.

But I've only left them in the oven for five minutes, and so they've received a certain amount of energy, but they've not reached the maximum temperature of the oven yet.

When you measure the temperature of those two blocks after leaving them in there for a while, the temperature might be different.

So Sophia did that, and she found that their temperatures were actually different to each other, instead of being the same.

After five minutes of heating in that same oven, she found that the block of copper had reached a temperature of 110 degrees Celsius, while the equivalent mass block of aluminium had reached only 50 degrees Celsius.

They both had the same amount of energy transferred to, they've both been heated in the oven and given the same amount of energy increase, but the temperature of the copper is increasing much more than the temperature of the aluminium, and that means that copper is easier to warm up than aluminium.

Let's check that you've understood what I've said there.

I've got two metals warmed up in the same oven for 10 minutes.

Which one had the most energy transferred to it? And you can see I've got a table of data there with copper and steel, and their final temperatures.

So pause the video, decide, and then restart, please.

Welcome back.

Hopefully you selected both about the same.

They're both placed in the same oven, and so they're both going to receive the same amount of energy through heating because they're in there for the same amount of time.

So well done if you selected that.

Now, the reason that the temperature increase is different for the two different metals is due to the nature of the particles in them and how they're bonded together with each other.

The particles in aluminium and in copper have different mass, so they're different sizes of particles overall.

And the attractive forces holding them together are different in the different metals.

So the forces between the copper particles and the forces between the aluminium particles are different strengths, and that means that they'll behave differently when you heat them up.

To increase the temperature of a substance, what you need to do is to make the particles in it vibrate more vigorously, faster.

The temperature is connected to the speed that those particles are oscillating about around their fixed positions, and it's harder to increase the vibrations of particles that have got more mass.

So it's more difficult to increase the vibrations of particles with more mass, but it's also to do with the forces holding them in place.

It's harder to increase the vibrations of particles with strong forces between them.

So it's the balance of those two things that will link to the increase in temperature, how much mass the particles have, and how strongly they're bound together.

Okay, a check for you now.

I'd like you to answer this true-or-false question, and then think of a reason why.

So, true or false, more energy is needed to increase the temperature of some substances compared to others? So pause the video and decide whether that's true or false, and then restart, please.

Welcome back.

Well, the answer to that was true, and now I'd like you to try and think of a reason why.

So pause the video, think of a reason why that statement was true, and then restart again, please.

And welcome back again.

The reason that's true is because the particles in the different metals or the different substances have different mass, and the particles in those metals or substances are also held in place with forces of different sizes, or stronger forces or weaker forces.

Well done if you thought of that answer.

Okay, what you're going to do to test these ideas is you're going to heat two different substances up, and you're gonna heat two different liquids up, providing them with the same amount of energy, but trying to measure the different temperature increases.

And to do that, you're gonna use this setup.

You're gonna use some water and some cooking oil, and heat them with a Bunsen burner and the rest of the heating apparatus.

So we're gonna have a beaker here on the top, and that's going to contain the liquid.

In this picture, I've put in 100 grammes of water, and that's on top of a gauze, which is on top of a tripod.

And then I have a Bunsen burner beneath it.

And you're going to use a flame to heat that water up and measure its increase in temperature, and provide a certain amount of energy by heating it for a certain amount of time.

In the experiment, you need to use the same mass of liquid each time.

So we're not going to measure the volume of the liquid, we're going to measure the mass of the liquid so that it's equivalent.

So I used 100 grammes of water, and in the second part of the experiment, I'll use 100 grammes of cooking oil.

To make sure that it's just the type of liquids that we're changing, we need to control some of the other variables.

We need to keep everything else in each of the two tests the same.

So we need to have the same starting temperature.

Each of the liquids is probably going to start at room temperature, so we'll try and measure that and make sure that that's the same for the start of each experiment.

We should use the same size of beaker in each instance because we're not just gonna be heating the liquid, we're also gonna be heating up that beaker, so we need the same size beaker in each test.

We should position everything exactly the same in each of the two tests as well.

And we should use the same type of Bunsen flame.

So once we've set the Bunsen flame, we shouldn't adjust it between the two experiments because that might mean that the flame was hotter in the second experiment than the first.

And we should also heat for exactly the same amount of time 'cause we want to provide exactly the same amount of energy in each of the two tests.

Right, let's see if you can identify the variables in the experiment when comparing liquids to see which is easiest to warm up, which are the control variables, which are the variables that need to be kept the same? So what I'd like you to do is select all of the control variables, pause the video, select all those variables, and then restart when you're done, please.

Welcome back.

And these are the things that we need to control.

We need to control the position of the beaker.

The starting temperature.

We don't control the final temperature.

We do control the time the liquid is heated for.

We need to heat them for exactly the same amount time.

We change the type of liquid.

And we need to control the Bunsen flame, using exactly the same strength of flame in both of the experiments.

Well done if you got all of those.

Okay, now it's time for you to carry out the experiment.

So we're gonna measure the temperature increase of water compared to the temperature increase of cooking oil when we provide the same amount of energy to each.

There's a method here.

We warm 100 grammes of water at room temperature for 100 seconds using a blue Bunsen flame, and we measure its final temperature with a thermometer.

Then we repeat the process using the same sort of apparatus with cooking oil.

And we must be very careful and make sure you don't spill any of the cooking oil, and make sure it can't get near the flame because the cooking oil is flammable, so be careful with it.

And after you've collected that data and measured the two temperature increases, you can answer these two questions.

Which liquid had the greatest increase in temperature and which liquid would need the most energy to increase its temperature by one degree C? So pause the video, carry out the experiments, and then restart when you're done.

Welcome back.

Well, here's the results of the experiment I carried out.

The final temperature of the water was 52 degrees Celsius, and the final temperature of the 100 grammes of cooking oil was 75 degrees Celsius.

And that means that the cooking oil had the greatest increase in temperature.

And from that, I realised that water needs more energy to increase its temperature by one degree C when compared to that cooking oil.

So well done if you got those answers.

Now it's time to move on to the second part of the lesson, and we're going to look at the thermal stores of different materials or different substances.

As we saw earlier in the lesson, it's easier to heat some substances than it is to heat others.

It takes longer for me to warm 100 grammes of aluminium up to 120 degrees Celsius than it does for me to heat 100 grammes of copper to that same temperature.

So I have to transfer more energy to the aluminium to get it up to the same temperature as the copper.

So, for example, my 100 grammes of copper, if I place it in an oven, it might take three minutes for it to reach 120 degrees Celsius.

But if I placed 100 grammes of aluminium into that same oven, it would take nine minutes, three times as long, to reach that temperature of 120 degrees Celsius.

We say that aluminium has a higher specific heat capacity than copper because it takes more energy to heat aluminium to the same temperature than it does copper.

So specific heat capacity is a measure of how difficult it is to heat a substance.

So I've got my 100 grammes of copper.

It requires three minutes to reach 120 degrees Celsius, and my aluminium takes nine minutes.

And that means it's taking three times as much energy to increase its temperature than it is for copper, so aluminium has the greater specific heat capacity.

Okay, let's see if you understand the basic idea of specific heat capacity.

Which of these metals below has the greater specific heat capacity? And I've got a table of three metals and also the time it takes to heat them up to a temperature of 60 degrees Celsius when I place them in a Bunsen flame.

And you can see the copper takes 32 seconds; iron, 42 seconds; and silver, 23 seconds.

So pause the video, decide which of those has the greatest specific heat capacity based on that data, and then restart, please.

Welcome back.

Hopefully you chose iron.

Iron takes longer to reach 60 degrees Celsius.

That means it's in the flame for longer and is receiving more energy, more heating.

And so it's got the highest specific capacity because it needs the most energy.

Well done if you got that.

And so we have more energy transferred by heating the 100 grammes of aluminium to 120 degrees Celsius than when heating the exact same mass of copper.

So we've got copper there.

It required three minutes to heat up to 120 degrees Celsius, and the aluminium required three times as long, nine minutes.

So it requires three times as much energy because it had three times as much heating in the oven to get to that temperature.

After heating, we can say that the aluminium has more energy in its thermal store than the copper.

So I've got equal masses of copper and aluminium, and the aluminium has more energy in its thermal store than copper when they're at the same temperature.

So my copper there has less energy than the same mass block of aluminium at the same temperature because they've got different specific heat capacities.

The aluminium, with its greater specific heat capacity, stores more energy in its thermal store than the copper is able to at the same temperature.

Okay, let's see if you understand the idea of thermal stores and energy in them.

Which of the metals below has the most energy in its thermal store at 60 degrees Celsius? And, again, I've got a table of heating data, how long it took to heat up to a certain temperature.

Pause the video, make your selection, and then restart when you're done, please.

Welcome back.

Hopefully you selected iron.

Iron took longer to reach 60 degrees Celsius, so it had more heating, it was heated for longer, so there was more energy transferred into it, so there's more energy in its thermal store.

Well done if you got that.

The more energy that's inside an object's thermal store, the more energy it can transfer to its surroundings or other objects it's in contact with.

So if I place a a metal ball I've heated up to a high temperature onto a block of wax, what's going to happen is there's going to be an energy transfer from the metal ball to the wax by conduction processes, or thermal conduction.

So the wax is going to heat up, and what will happen is the ball will melt the wax beneath it and sink into it.

So we've got a transfer of energy from the ball to the wax.

The metal ball's thermal store is decreasing and its temperature will fall so it will become cooler.

And the wax's thermal store will increase because energy's being transferred into the wax, and so it will melt.

Okay, another check for you here.

I've got two balls.

They're at the same temperature of 150 degrees Celsius and they're both placed on a big sheet of wax, as shown in the picture there.

And you can see that the balls have sunk into the wax at different distances.

What do those results show? So read through the answers and decide which of those there is.

So pause the video, make your selection from those four answers, and then restart when you're done, please.

Welcome back.

Hopefully you selected answer B.

The steel has more energy in the thermal store than the lead when they're at the same temperature.

And you can tell that because the steel has been able to melt more of the wax.

It's been able to transfer more energy to its surroundings into the wax, melt more of it, so it must have had more energy in its thermal store in the first place.

Also, it tells us that steel has a specific heat capacity that's higher than that of lead, 'cause they're both the same mass and they're both the same temperature, but the steel ball had more energy stored in it, so it must have had a greater specific heat capacity.

Well done if you selected those two answers.

Okay, it's time for the final task of the lesson.

And I've got two metal blocks again, of the same mass, and they're both heated to the same temperature.

So there's a 50-gram cube of lead, 50-gram cube of steel, heated up to 80 degrees Celsius in a beaker of hot water.

And then they're put into a new beaker with 100 centimetres cubed of cold water.

What I'd like you to do is to think what happens next.

So I'd like you to answer those two questions and explain your answers, please.

So pause the video, answer those two questions, and restart when you're done.

Okay, welcome back.

And what will happen here is the steel cube will warm the water more than the lead cube, and that's because steel has a higher specific heat capacity.

And that means it's got more energy stored in its thermal store and it'll be able to transfer that energy to the water and, therefore, heat up the water more.

So the water will increase in temperature more from the steel than it can from the lead.

The steel cube will increase the temperature by about 30 degrees Celsius compared to the lead because it's got a specific heat capacity about three times higher than that of lead.

So it can transfer about three times as much energy to the water.

Well done if you got answers like that.

Okay, we've reached the end of the lesson, and here's a summary of everything we should have learned.

It's easier to increase the temperature of some substances by heating than it is other substances, and that's because the particles in one substance are different to the particles of another substance.

They can have different masses and they can have different strengths of attractive forces holding the particles together.

If more energy needs to be transferred to increase the temperature of a substance by the same amount, it's got the higher specific heat capacity.

And if two substances have the same mass and the same temperature, the substance with the higher specific heat capacity has more energy in its thermal store.

Well done for reaching the end of the lesson.

I'll see you in the next one.