Lesson video

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

This lesson's called, Energy and Temperature, and in it, we're going to be discussing the difference between the temperature of something and the energy in its thermal store.

By the end of this lesson, you're going to be able to describe the difference between temperature and the energy and some of the factors that affect the amount of energy stored in an object and how that's related to temperature and other factors like mass of the object.

Here are the keywords and phrases that'll help you in the lesson.

And a random process is something that happens or is chosen without any specific pattern.

So there's no plan to it.

Random events are unpredictable.

They'll just happen in an unpredictable order.

A temperature of an object is a measure of how hot or cold something is, and it's a comparison between objects.

We can say one object is hotter than another object.

And a thermal energy store is the energy a substance has because of the random motion of the particles within it.

So that's a thermal energy store.

This lesson's in three parts and in the first part we're going to be looking at the relationship between the temperature of an object and the behaviour of the particles within that object.

The next part of the lesson, we're going to look at the energy of hot objects and how that energy changes when an object becomes hotter, it's at higher temperature.

And in the final part of the lesson, we're going to look at the energy as stored in an object and its size, its mass, so the energy of larger objects.

So let's start by looking at the relationship between temperature and particle behaviour.

All matter is made up of tiny, tiny particles and the spacing between those particles depends on whether that material is a solid, a liquid, or materials in a gaseous state.

So I've got a bottle here and the bottle is made of solid material plastics and glass, but it contains some liquid water and some air which is a gas.

And you can see the bottle cap of the bottle that's a solid.

And the particles have got very small spaces between, they're very tightly packed together.

The gas that's got very large spaces between the particles, the particles are much more spaced out in than they are in any solid material.

And the liquids got the particles fairly close together.

There's small space between them.

The arrangement of the particles in a solid is different than the arrangement of the particles in a liquid and a gas.

Particles in a solid are generally in a regular arrangement.

There's a repeating pattern where the particles follow set positions.

The particles in a gas, they're in random arrangement.

They don't have an overall pattern at all.

They're just in random directions.

And the same with liquid.

The particles are also in random arrangement, there's no overall pattern to them.

Let's check if you understood those ideas.

Which of those diagrams shows the arrangement of particles in a liquid? So pause the video, make your selection from those three, and then restart please.

Welcome back, hopefully you selected C.

You can see there that the particles are fairly closely packed together and they're in a random arrangement and that's what a liquid is.

So well done if you selected C.

Now the particles in solid liquids and gases are in constant motion and that motion is random.

The particles are moving in random directions, all different directions at all times.

So you can see I've got my solid, liquid, gas here again in the bottle and in a solid, the particles are just vibrating in random directions.

If you watch those for a while, you can see that the particles jiggle about, but they don't move from their position overall.

The particles in a liquid and in a gas they are moving more quickly and past each other.

They're not in fixed positions.

They drift around.

So they're in random motion where the particles can flow past each other.

Okay, what I'd like you to do is to answer this, I've got solids, liquids, and gases, and I'd like you to put a tick in the box if those particles match the statement.

So in which state do the particles have a random arrangement? I'd like you to put a box, sorry, a tick in the boxes to the right of that please.

And in which states do the particles move in random directions? So you'll be putting several ticks in there.

So pause the video, put the ticks in the right boxes, and then restart please.

Welcome back, well for the first part of that question, the particles in a random arrangement, well, liquids and gases both have a random arrangement.

So well done if you've got those two.

And the particles moving in random directions, part of the question, well all of them.

So all of them have particles that move in random directions.

Well done if you've got those as well.

Now let's look at the relationship between temperature and the random motion of the particles.

So I've got a scale here and this is a scale for water.

And you can see I've got solid water, which is below the freezing point, that's zero.

And liquid water, which is above the freezing point.

And I'm going to show you the particle motions at a range of temperatures.

So I've got here the particles in solid water, although it's a freezing point, those particles are moving around randomly, but they're just vibrating that it's a solid material.

And so the particles just vibrate in place.

Above the freezing point above zero, the particles are free to move past each other.

They're in the liquid state.

And as you can see, the particles that are higher temperature are moving faster.

The more I increase the temperature of the liquid water, the faster those particles move in the random directions.

When the particles are moving at high speed, when they're moving faster, they'll push each other further apart.

So if I could examine the spacings between the particles at different temperatures, I'd see something like this.

So let's look at the bottle cap first.

The solid, as you can see at low temperature at 20 degrees C, the plastic top, the particles are very tightly packed together.

But if I heated that top up, the particles would move slightly further apart 'cause they'd be vibrating faster, taking up more space.

So the particles in the solid move further apart.

The particles in the liquid do the same sort of thing at a lower temperature at 20 degrees C, the particles are quite closely packed together, but as I heat them up, they move very slightly further apart.

And you might notice that by seeing actually that the level of the water in the bottle will rise very slightly as I heated it because the water would expand.

Okay, let's check if you understood that idea.

An aluminium bottle cap expands if you put it into hot water.

What happens when it expands? And what I'd like you to do is to select the two correct answers from the list of four there.

So pause the video, select two answers, and restart please.

Welcome back, hopefully you selected these two options.

The particles are going to vibrate faster and the bottle cap is going to get wider.

And that's because the particles are going to move further apart.

So well done if you've got those two.

Now let's look at what happens to a gas when you heat it up.

So we can see from a gas that the particles move further apart more clearly than we can see in solids and in liquids.

So I've got a bottle here and it's full of trapped air and I've put a balloon over the top and that's going to act as a bottle cap, but it's a flexible one.

It will be able to stretch and contract.

And if I place that bottle into some hot water, so I've put it in some very hot water here, the air expands and as it expands, it takes up more space and it fills that balloon causing the balloon to inflate.

So heating a gas causes it to increase in volume quite dramatically, much more than for a solid and for a liquid.

If we imagine the particles inside the gas, we can see what's happening.

And so I've got my gas here inside the bottle and I've drawn just a few of the particles that are in it and they're moving around in random motion.

And what happens when I put it into hot water is that those particles start to move faster in the random motion and they're going to push harder on the surfaces of the bottle and the balloon.

And that's going to stretch the rubber in the balloon.

And that's what makes the balloon expand.

So the gas has expanded because the particles are moving faster and that makes it occupy more space overall.

Okay, let's see if you understand that.

What happens to the particles in a gas if you increase its temperature? And I'd like you to select the two correct answers here, please.

So pause the video, make your selection, and then restart.

Welcome back, hopefully you selected these two options.

The particles will move faster and they'll collide with things with more force 'cause they're moving faster.

Well done if you've got those two.

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

And in it I've got two questions.

First of all, I'd like you to draw the particle arrangements for a solid, a liquid, and a gas.

And then for part two, how does the movement of the particles and the spacing between them change when you increase the temperature of a solid and then a liquid and a gas? So pause the video, answer those two questions and restart when you're done please.

Welcome back, here are my answers to those questions.

So I've drawn my solid, liquid and gas there.

And for the heating part of the question, in a solid, the particles will vibrate faster and further.

So it'll take up more space as you increase the temperature.

And in a liquid or a gas, the space between the particles will increase as well when you increase the temperature because the particles are moving faster and colliding with each other more often.

Well done if you've got those.

And now it's time for the second part of the lesson.

And in it we're going to be looking at the relationship between energy and temperature.

The energy of hotter objects.

If an object's got energy, it can do a useful job for us.

So hot water has energy 'cause it can keep us warm, we can use it for heating other things.

It has more energy than the same amount of cold water.

So I've got a hot water bottle here and I've got cool water in one that's got less energy than the one that's at higher energy, sorry, a higher temperature that's got more energy in it.

If we heat a substance, what we're doing is transferring the energy to it.

One of the ways we heat water is in a kettle.

So I've got some water inside a kettle here with a plastic casing and a handle and there's an electric heater at the bottom that's made of metal.

And if I pass an electric current to that, that will heat it up.

So the electric heater at the bottom will be at very high temperature due to an electric current in it.

And that's going to cause the water to heat up because that's in contact with that metal surface.

So the particles in the metal are going to be vibrating very quickly 'cause they're at high temperature.

And any water particles that come in contact with the metal, they're going to collide with it and they're going to gain energy.

They're going to start moving faster because of the collision with the vibrating metal particles.

And so gradually the water temperature is going to increase as the particles in the water gain energy and start moving faster.

So the faster the particles are moving, the higher the temperature of the water.

The longer you heat the water for, the more energy you're going to give it.

So if I've got a kettle and I turn it on for one minute, the water might reach a temperature of 40 degrees Celsius.

But if I leave that kettle on for a longer period of time for two minutes, say, then the water temperature's going to increase more.

It's going to be a higher temperature.

And if I leave it on for even longer, it's going to be a higher temperature again.

So providing it with more and more energy, the less energy the water has, the lower it's temperature, the more energy it has, the higher its temperature.

So there's a relationship between temperature and energy.

Higher temperature means there's more energy stored in the water.

When you stop heating the substance, then you're going to stop transferring energy to it and its temperature's not going to increase anymore.

So I've got a graph here of the temperature of water in the kettle and I turned it on the temperature started at 20 degrees Celsius and I left it on for four minutes.

And the temperature gradually roses to 100 degrees C, the boiling point of water you can see there.

And kettles, once the water reaches 100 degrees C, they're designed to turn off automatically.

So they're not going to continually boil the water forever.

They're going to switch off and not use up any more electricity.

So the kettle automatically turns off when the water reaches 100.

What's going to happen then is the water's going to gradually cool, so it's going to cool slowly because it's inside an insulated kettle.

The kettle's made of plastic, that's designed to be a poor thermal conductor, a thermal insulator.

And so it's not going to allow the water to cool very quickly.

So the water there is cooling slowly.

The higher the temperature of a substance, the more energy is stored in its thermal store.

So I've got some water here and you can see the particle behaviour at 20 degrees C.

The particles aren't moving particularly fast, but at its boiling point, at 100 degrees C, the temperature of the water is much higher and the particles are vibrating much, much more.

So at a low temperature, there's less energy stored in the water, at a higher temperature, there's more energy stored in that water's thermal store which is connected to the particles moving around.

So I'd like you to answer a question about that please.

Compared to water at room temperature, which energy store does hot water have more energy in? So pause the video, decide which of those stores there's more energy in because the water's hotter and then restart please.

Welcome back, hopefully you selected thermal store.

The thermal store of hot water is greater than the thermal store of cold water.

Well done if you've got that.

So as a hot object cools, the energy in its thermal store is decreasing.

So I've got a hot object here.

I've got hot water inside a hot water bottle.

It's at 60 degrees C.

And over a period of time what's going to happen is that water's gradually going to cool.

So the temperature's going to decrease.

And a few hours later that water will have cooled down to something like 20 degrees Celsius.

So there's less energy in that hot water bottle now the energy's been dissipated or spread out into its surroundings.

The rate of cooling or how quickly the energy decrease happens depends upon what the object's surrounded by.

So I've got another hot water bottle here.

And this hot water bottle has got a wool cover on it.

And wool is a thermal insulator.

So it reduces the rate of energy escaping from the water.

And so the hot water bottle's going to stay hotter for longer when it's wrapped in an insulator.

Now that energy that is being transferred from the thermal store of the water isn't lost as that water cools, that energy is being transferred to whatever object are in contact with that hot water bottle.

And that might be a person or blanket or the air itself.

So the hot water bottle is cooling down, but at the same time it's warming up the surroundings, the objects that are surrounding it.

Okay, a question for you now.

When a hot object cools down, what happens to the energy in its thermal store that goes to the surroundings? So we've got energy of the hot object and energy of the surroundings, and I'd like you to decide if the energy of those two things goes up or down as the hot water bottle is cooling.

So pause the video, make your selections and restart please.

Welcome back, well, the energy of the hot object, the hot water bottle in our examples earlier, that's going down and at the same time the energy of the surroundings is going up.

So well done if you selected those two.

Okay, now for the second task of the lesson, I'd like you to complete these statements using just the words more or less.

So pause the video, fill in the gaps, using more or less, and then restart when you're done please.

Welcome back, here are the answers to those.

So compared to water at room temperature, hot water has more energy in its thermal store.

Heating water gives it more energy.

After hot water cools, it has less energy, and the better the insulation around the hot object, the less quickly the energy is transferred to the surroundings.

Well done if you've got those.

And now it's time for the third and final part of the lesson.

And we're going to look at the relationship between the thermal energy store of an object and how large it is, how massive it is.

So let's do that.

So the first thing I need to point out is energy is not the same as temperature.

There is a relationship between energy and temperature, but they're not the same thing.

The more of a substance there is at one temperature, the more energy it has.

So you can have two objects like this.

So I've got a hot water bottle here and another larger hot water bottle and they're at the same temperature, but one of them has more energy than the other.

The one with the greater mass of water in it has more energy than the one with a smaller mass of water.

So more hot water will keep you warmer for longer.

The more there is of a solid, liquid or a gas, the more energy there is for the same temperature.

So I've got a kettle here and I'm going to heat some water up for two minutes and it's going to get to 100 degrees C.

But if I've got more water in that kettle, then I'm going to need to heat it for longer to provide it with more energy to get that up to 100 degrees C, 'cause there's more water in it.

I need to provide more energy to increase its temperature to the same temperature, so it's boiling point 100 degrees C there.

So it depends upon how much mass of water I've got in the kettle, how long it's going to take it to boil.

Let's see if you understand that concept.

If it takes a kettle four minutes to boil water for four cups of tea, how long is it going to take to boil enough water for just one cup of tea? So pause the video, make your selection from the answers there, and then restart please.

Welcome back, hopefully you selected A, one minute.

There's a quarter of the amount of water needed.

So there's a quarter of the amount of energy, so it's going to take a quarter of the amount of time, so just one minute.

Well done if you selected that.

So as we've seen, it takes more energy to warm up a substance to a particular temperature if there's more of it because there's more mass, there's more particles inside that particular substance, and so we need more energy to get them all to the same temperature.

So imagine one single cup of tea has a huge number of particles in it.

You can see the number there, but two cups of tea or water, it's going to have twice as many particles in it.

And I'm going to have to increase the energy of every single one of those particles.

So it's going to take more energy to heat up a greater mass of water.

Okay, I've got three examples of thermal stores here.

I've got three bowls of porridge and they're all at the same temperature, but daddy bear's got more porridge.

Mommy bear the middle amount of porridge and baby bear the smallest amount of porridge, the smallest, mass of porridge.

So which of those three bears porridge has got the most energy in its thermal store? Pause the video, make a selection and restart please.

Welcome back, hopefully you selected option A.

There's a greater mass of porridge there, even though they're all at the same temperature.

That greater mass of porridge means that that bowl of porridge has got the most energy in its thermal store.

Well done if you've got that.

Now one thing to look out for is the fact that objects at higher temperatures might have thermal stores that contain less energy than objects at much lower temperatures.

So imagine I've got a match here and that's at a very high temperature at 800 degrees C and a bath full of just warm water.

It's only at 40 degrees C.

Well actually the very hot flame, the match has got much less energy than the bath full of water.

And the bath full of water has got a much greater mass and much higher volume of water.

And it's got a much larger thermal energy store than the flame.

Even though the flame is at a higher temperature.

The less energy that's in the thermal store of an object, the less energy it's going to be able to transfer to something else to warm it up.

So I've got a bath here, it's at 40 degrees C, and if I just put a hot match in it, it's not actually going to increase the temperature of that water very much because the burning match had a very small thermal energy store.

So you wouldn't even be able to measure the temperature rise of the water.

It'd be so small if I just use a single match to try and heat that water up.

So it started at 40 degrees C and you wouldn't be able to notice a temperature, it wouldn't even go up to 41 degrees C if I put a hot match in it.

Okay, let's see if you understood that idea.

Which of the three bears has porridge with more energy in one spoonful than a porridge at 30 degrees C? So pause the video, make your selection, and restart please.

Welcome back, hopefully you selected two options, daddy bears porridge, which is at 75 degrees C.

That would have more energy per spoonful and baby bears porridge as well.

That's got at 45 degrees C, that would have more energy in its thermal store per spoonful than mummy bear.

So well done if you've got those two.

Okay, time for the final task of the lesson.

And I'd like you to complete a few more sentences please.

So I'd like you to only use the word energy or temperature to fill in the gaps of each of these five sentences.

Pause the video, fill in those gaps, and then restart when you're done please.

Welcome back, and here's the answers to those.

A thermometer measures temperature.

Particles in an object move faster if the temperature is higher.

The temperature of a flame is higher than that of a bath of warm water.

The energy of a bath of warm water is higher than that of a flame.

And adding water at 40 degrees C to a cup of water at 40 degrees C increases its energy.

The total amount of energy in it, it won't change its temperature.

So well done if you've got those correct.

Okay, we're at the end of the lesson.

And here's a summary of everything.

We need to give an object energy to increase its temperature.

So providing energy by heating increases temperature.

The higher the temperature of an object, the faster its particles move in random directions and the bigger the space between those particles as well.

It takes more energy to warm up more of a substance to a particular temperature because there are more particles and we have to provide energy to each of those particles.

And the more energy an object has in its thermal store, the more energy it has to transfer to other objects so it can provide more energy to other objects and want them.

Well done for reaching the end of the lesson.

I'll see you in the next one.