Welcome to today's lesson on Exothermic and Endothermic Reactions.

It's part of the unit Fuels and Energetics.

My name's Mrs. Mytum-Smithson and I'm so pleased that you've come along to learn with me today.

During this lesson, we're going to look at two keywords, exothermic and endothermic.

Don't worry if you don't know about these words because by the end of the lesson you should be able to identify whether a chemical reaction is exothermic or endothermic and explain how you know.

Today's keywords are: exothermic chemical reaction, endothermic chemical reaction, and dissipate.

On the next slide, there's some sentences that include these keywords, so pause the video and have a read if you wish to do so.

Then press play when you're ready to start learning in the lesson.

Today's lesson consists of two learning cycles, Exothermic and Endothermic, and then we're going to move on to Identifying Exothermic and Endothermic Reactions.

So let's get going with our first learning cycle, Exothermic and Endothermic.

An exothermic chemical reaction is a type of reaction in which energy is transferred to the surroundings from their reactants.

So if we have a think about that, this is when the temperature of the surroundings will increase during that chemical reaction.

So here's some examples.

We've got combustion, that's a science word for burning.

You can see here this match is on fire.

We've got neutralisation.

That's to do with acids and alkalis.

And we've also got a displacement reaction.

So here you can see that silver is appearing on that copper wire and that's to do with displacement.

So all of these are exothermic chemical reactions.

So energy is transferred to the surroundings from the reactants.

Exothermic reactions can be found in everyday items like single use hand warmers or a self heating meal.

Here we've got a picture of some self heating noodles.

That white packet in the middle, that is the exothermic reaction, that's where that's taking place.

And the arrows show the direction of the energy transfer from the chemical reaction in that heating pack to the surroundings.

So the surroundings in this case are the noodles.

Once they're placed on top of the heating pack, they will then heat up and you've got a nice, hot, noodly meal.

A quick check for understanding.

Which image best represents an exothermic reaction? So we've got an image of a thermometer before the reaction takes place, and then we've got the reaction taking place in the flask.

And I want to know what happens to the thermometer.

Does it go down like in picture A, stay the same like in picture B, or increase like in picture C? Pause the video for some thinking time.

Press play when you've got your answer.

Well done if you said C.

C represents an exothermic reaction, the temperature on the thermometer has increased.

What I'd like you to do now is select two options.

In an exothermic reaction, energy is transferred from the reactants to the surroundings or from the surroundings to the reactants.

The temperature of the surroundings increases.

The temperature of the surroundings decreases.

Pause the video now for some thinking time.

Press play when you've decided on your answers.

Well done if you said A and C.

In an exothermic reaction, energy is transferred from the reactants to the surroundings causing the temperature of the surroundings to increase.

Well done if you got both of those correct.

After an exothermic reaction has taken place, the thermal energy dissipates into the environment from the reaction mixture.

So the environment is wherever that reaction is taking place.

The room.

For example, a classroom or a laboratory or even outside.

As the environment is so large, the thermal energy increase only has a very, very small impact on the temperature of the room.

So the temperature of the room is not going to increase greatly or substantially just because you've got a small exothermic reaction.

So we just say that the thermal energy dissipates into the environment.

Now I've got a check for understanding for you.

A small amount of magnesium powder is added to a test tube containing copper sulphate solution.

The temperature of the reaction mixture increases.

The reaction finishes and the test tube is left.

What will happen to the temperature of the reaction mixture in the test tube? Will it gradually decrease, will it remain the same or will it continue to increase? Pause the video now for some thinking time, choose your answer and then press play and I'll let you know if you're right or not.

Well done if you said gradually decrease the reaction mixture in the test tube.

The temperature for that will gradually decrease.

Now I want you to explain why.

So is it because the reaction will keep heating the reaction mixture? Energy is transferred to the environment? Or energy is transferred from the environment? Pause the video for some thinking time and press play when you've got your answer.

Well done if you said B.

Energy is transferred to the environment, so that's to the classroom.

An endothermic chemical reaction is a type of reaction which energy from the surroundings is transferred to the product of the reaction.

Let's have a look at some everyday examples.

Photosynthesis.

So that is an endothermic reaction.

Electrolysis is an endothermic reaction.

And here's the thermal decomposition of copper carbonate.

If you look very carefully at this reaction, you should see it starts off green and then as it's being heated, it changes to black, and that is an endothermic reaction, the thermal decomposition of copper carbonate.

Endothermic reactions can be found in some everyday items, such as self cooling drinks or an instant ice sports injury cool pack.

So here's a picture of one of those, a cool pack.

Once you've activated it, the arrows then show the direction of energy transfer from the environment, So that's the injured body part, to the chemical reaction in the cooling pack.

Which image best represents an endothermic reaction? So here's the thermometer before the reaction takes place.

And then as the reaction is taking place, what happens to the thermometer? Does the temperature decrease, does it stay the same, or does it increase? Pause the video now for some thinking time.

Press play when you've got your answer.

Well done if you said A.

A is correct.

Energy would be transferred from the surroundings into the reaction mixture, therefore the temperature would decrease.

What I want you to do for this check for understanding is select two options.

In an endothermic reaction, energy is transferred from the surroundings to the chemicals.

From the chemicals to the surroundings.

The temperature of the surroundings increases.

The temperature of the surroundings decreases.

Pause the video while you have a think and then press play and I'll tell you the answers.

So, well done if you've said in an endothermic reaction, energy is transferred from the surroundings to the chemicals and the temperature of the surroundings decreases.

Well done if you got that right.

After an endothermic reaction has completely finished, the thermal energy from the environment transfers to warm the reaction mixture to the classroom temperature.

So as the environment is so large, the thermal energy decrease only has a very, very small impact on the temperature of the room.

So here's the environment, that's the classroom there.

You can see the energy is transferred from the environment into the reaction mixture.

That's going to cool the classroom slightly, but very, very, very slightly.

So it's not going to have a large impact on the temperature of the room.

I've got a check for understanding for you now.

A spatula of citric acid is added to a test tube containing sodium hydrogen carbonate solution.

The temperature of the reaction mixture decreases.

The reaction finishes and the test tube is left.

What will happen to the temperature of the reaction mixture in the test tube? Will it continue to decrease, remain the same, or gradually increase? Pause video, choose your answer, then press play and I'll let you know if you're right.

Well done if you said gradually increase.

Now I'm going to ask you to give me a reason for that.

So explain your answer.

The reaction will keep cooling the reaction mixture.

Energy is transferred to the environment.

So that's the classroom.

Energy is transferred from the environment.

Pause the video now and have a think.

Press play and we'll go through the answer.

Well done if you said energy is transferred from the environment.

So that will gradually warm up that reaction mixture.

Here's part one of Task A.

During an exothermic reaction, the temperature of the chemicals in the test tubes increases.

You can see there I've got a picture of what's going on, our setup.

So we've got our reaction mixture there, our thermometer and the test tube.

When the reaction is finished, the test tube contains a chemical mixture of the products of the reaction, any unreacted reactants and water if the chemicals are in solution.

The chemicals then gradually cool until they're at the same temperature as the environment.

So that's the classroom.

What I want you to do is just have a five second think about what's going on.

So pause the video, have a think about what's going on, and on the next slide I've got some questions for you to answer.

What I want you to do for this task now is fill in the gaps to explain what happens when chemicals cool down.

You should only use the words "temperature" and "energy" in the spaces.

So in an exothermic reaction, the chemicals react in the test tube and their what is released? The something of the reaction mixture, the surroundings increases.

Once all the chemicals have reacted, no more something is released.

The reaction mixture will start to cool as the something will dissipate into the environment.

That's the classroom.

Eventually the what of the reaction mixture reaches the same something as the environment.

So pause the video now while you complete all those gaps with only the words "temperature" and "energy", then press play and we'll go through the answers together.

Well done for completing that task.

Let's have a look and see if you were right or not.

So here's the first sentence.

In an exothermic reaction, the chemicals react in the test tube and their energy is released.

The temperature of the reaction mixture, that's the surroundings, increases.

Once all the chemicals have reacted, no more energy is released.

The reaction mixture will start to cool as the energy will dissipate into the environment, that's the classroom.

Eventually the temperature of the reaction mixture reaches the same temperature as the environment.

Well done if you've got that one correct.

Here's part two of Task A.

Very similar to part one, but this time we're going to do about endothermic reactions.

So during an endothermic reaction, the temperature of the chemicals in the test tube decreases.

When the reaction is finished, the test tube contains a chemical mixture of the products of the reaction, any unreacted reactant and water if the chemicals are in solution.

The chemical mixture then gradually warms until they are at the same temperature as the environment.

That's the classroom.

Think about what's going on.

So pause the video and then press play when you're ready to complete the next part of the task.

What I want you to do now for part two of Task A is fill in the gaps to explain what happens when chemical reactions warm up.

And you should only use the words "temperature" and "energy" to complete these gaps.

So, in an endothermic reaction, the chemicals react in the test tube and the what of the surroundings is transferred to the products formed.

The something of the reaction mixture, that's the surroundings, decreases.

Once all the chemicals have reacted, no more what is transferred? The reaction mixture will start to warm up to room temperature as the something from the environment, that's the classroom, will transfer into the reaction mixture.

Eventually the something of the reaction mixture reaches the same something as the environment.

Pause the video while you fill in those gaps, then press play and we'll go through the answers together.

Well done for completing that task.

Let's see how many you got correct.

So in an endothermic reaction, the chemicals react in the test tube and the energy of the surroundings is transferred to the products formed.

The temperature of the reaction mixture, that's the surroundings, decreases.

Once all the chemicals have reacted, no more energy is transferred.

The reaction mixture will start to warm up to room temperature as the energy from the environment, that's the classroom, will transfer into the reaction mixture.

Eventually the temperature of the reaction mixture reaches the same temperature as the environment.

So well done if you've got all of those correct, you're doing really well.

We've completed the first learning cycle of Exothermic and Endothermic.

Now we're going to look at Identifying Exothermic and Endothermic Reactions.

Now we're going to carry out an experiment, and first of all, we're going to look at the equipment we're going to use.

So we've got a beaker, and inside that beaker we're going to place a polystyrene beaker.

The reason why we place a polystyrene beaker inside that beaker is so that the polystyrene beaker doesn't tip over when you add the thermometer.

Once you've added the thermometer to that, you're then going to add reactant 1.

Then we're going to have a look at the full method.

So the first thing you're going to do is you're going to set up that equipment as shown in the diagram.

You're going to add reactant 1 into the polystyrene beaker.

You're going to measure and record the temperature.

So that's the start temperature.

You're going to add reactant 2 and then you're going to stir.

Then finally, you're going to measure and record the highest or the lowest temperature, and that's called your end temperature.

So this is how you're going to identify an exothermic or endothermic reaction.

A quick check for understanding.

You should measure and record the temperature only before reactant 2 is added.

Only the highest or lowest temperature after reactant 2 is added.

Or before reactant 2 is added and the highest or lowest temperature after reactant 2 is added.

Pause the video for some thinking time and press play and we'll go through the answer.

Well done if you said C.

You need to measure and record the temperature before reactant 2 is added, and also the highest or lowest temperature after reactant 2 is added.

Well done if you got that correct.

For part one of Task B, you're going to carry out the practical and complete the results table.

Your teacher will go through all the safety that you need to do when carrying out this practical.

Pause the video, carry out the practical, complete the results table, then press play and we'll go through some results.

Here's a set of results that I've carried out.

So for the start temperature, that was going to be 25 degrees 'cause I've got a nice, warm lab.

The end temperature was 32.

So all I've got to do then to calculate the temperature change is take the end temperature and subtract from that the start temperature, and that should leave me with seven and because that's a positive seven, that is an exothermic reaction.

Let's have a look at the next one.

So again, the lab with 25.

Ended at 18.

So you're going to do the calculation here, and this time you'll see that the temperature change is minus seven.

So the temperature there decreased.

That means that it is a endothermic reaction.

Let's have a look at the next one.

Copper sulphate and magnesium powder.

We've got 27 and 47, so quite a high end temperature there.

A temperature change of 22, that means it's exothermic.

Then we've got sulfuric acid and magnesium ribbon.

Again, we're going to carry out the same thing there and we're going to see that the temperature change is positive.

So that's a exothermic reaction.

So well done if you've managed to get the same results as me.

Here's part two of Task B.

Izzy has carried out some reactions.

Using her results, calculate the temperature change and decide which reactions are exothermic and which ones are endothermic.

So pause the video now, calculate those temperature changes, state whether it's exothermic or endothermic, then press play and we'll go through the answers.

Well done for completing task two.

Let's have a look at the answers.

So here, the temperature change, 34, subtract 25 equals nine.

So that means that the reaction mixture is increased by nine degrees Celsius.

So that means that that one is exothermic.

Well done if you got that one.

Reaction number two is negative 15.

So that's the opposite, isn't it? Because the temperature has decreased.

So that means that that is an endothermic reaction.

Then we'll have a look at number three.

That one is positive 27.

So that is an exothermic reaction.

And finally, this one is negative 18 temperature change.

So that means that that is an endothermic reaction.

Energy is being transferred from the surroundings to the reaction mixture.

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

Here's a summary for today's lesson.

An exothermic chemical reaction causes an increase in temperature, an endothermic chemical reaction causes a decrease in temperature.

An exothermic reaction transfers energy from the reactants to the surroundings, an endothermic reaction transfers energy from the surroundings to the products.

Well done for working really hard this lesson.

I hope you're now much more confident about using the terms endothermic chemical reaction and exothermic chemical reaction.

I hope to see you again sometime soon.