Hello, I'm Mrs. Adcock and welcome to today's lesson on combustion of alcohols, and this lesson is focused on the practical.

We are going to be collecting calorimetry data and thinking about how we can analyse that calorimetry data to determine if different alcohols release a different amount of energy during combustion.

In today's lesson, the lesson outcome is I can analyse calorimetry data to determine which alcohol releases the most energy when combusted.

Some of the keywords that we will come across during today's lesson include alcohols, combustion, calorimetry, and independent variable.

Here you can see each of those keywords written in a sentence.

It would be a good idea to pause the video now and read through those sentences.

You might also like to make some notes so that you can refer back to them later on in the lesson if needed.

Today's lesson on combustion of alcohols is split into two main parts.

So the first part of today's lesson, we are going to be looking at collecting calorimetry data and thinking about how we can record our data.

Then we're going to move on to looking at analysing our calorimetry data.

Let's get started on collecting calorimetry data.

Jacob wants to investigate how the type of alcohol affects the energy released during combustion.

Now, alcohols are a homologous series of compounds that contain the OH functional group.

So some examples of alcohols would be methanol, ethanol, propanol, and butanol.

And Jacob wants to know if we use different types of alcohols, how this affects the energy released during combustion.

And Jacob's got a prediction there.

He says, "I predict that different alcohols will release different amounts of energy during combustion." Do you think that Jacob's prediction is correct? And why do you think that? You may agree with Jacob that different alcohols will release different amounts of energy during combustion.

Or you may think that all alcohols will release the same amount of energy during combustion.

We are going to collect some calorimetry data and then analyse this to work out whether Jacob is correct and whether the type of alcohol does affect the amount of energy that is released during combustion.

Calorimetry is an experiment that we can use to measure the amount of energy that is released when fuels combust.

Calorimetry can be used to indirectly measure the energy released from the combustion of different alcohols.

When we talk about combustion, we mean that these alcohols are going to react with oxygen, and during this process, energy is going to be released.

So combustion is an exothermic process.

We can see the equipment there that we use for calorimetry.

So we've got the thermometer and a known amount of water placed in our calorimeter.

This is then held by a clamp and a clamp stand.

And underneath our calorimeter, we have our alcohol burner, which is placed on a heatproof mat.

The calorimetry data should be presented in a table of results, and the headings for a table of results are always the dependent and the independent variables.

The dependent variable is the variable that you measure or observe to get your results, and the independent variable is the variable that you change or select your values for.

Here we can see an example of a results table.

We have the independent variable in one column and the dependent variable in another column.

For both the independent variable and the dependent variable, we record the units if necessary.

Control variables are not recorded in a table of results because they do not change.

The control variables are the variables that must remain the same throughout an investigation.

Here is an example of what a results table might look like for calorimetry data.

We've got a column sharing the type of alcohol.

We've got the initial mass of the burner and the final mass of burner both recorded in our table and they are measured in grammes.

We have the initial temperature of the water and the final temperature of the water in the calorimeter, and these are measured in degrees Celsius.

The dependent and independent variables are used as the headers and the units are shown.

Time for a check for understanding.

Laura has produced the table below for calorimetry.

What mistake has she made? She has the type of alcohol in one column and the volume of water measured in centimetres cubed in a second column.

What mistake has Laura made? Is it A, the units are missing? B, the independent variable is missing.

C, a control variable is included.

There may be more than one correct answer, so choose any options that you think are correct.

A mistake that Laura has made is to include a control variable.

So the volume of water is a control variable because we keep this the same throughout the investigation.

Answer A, the units are missing, is incorrect because for our type of alcohol, we do not have units and she has included the units for the volume of water.

The independent variable is missing.

That is also not correct because she has included the independent variable because the independent variable in this investigation will be the type of alcohol.

Laura needs to improve her results table by including the data for the initial mass of the burner, the final mass of the burner, the initial temperature of the water, and the final temperature of the water.

So Laura is missing the dependent variable data from her results table.

For our first practise task of today's lesson, you need to first of all follow a calorimetry method to collect data for the combustion of different alcohols, and you are going to record your data in a results table similar to this one you can see on your screen.

Let's have a look at the calorimetry method that you might follow.

So first of all, measure the initial mass of the alcohol burner.

It's important that we know the initial mass so that when we later on record the final mass of the alcohol burner, then we can work out the amount of alcohol that has combusted.

We are going to place the alcohol burner directly below the calorimeter.

It is important that you keep the distance between the wick and the calorimeter the same throughout the investigation.

This is one of our control variables.

We are going to place 50 centimetres cubed of water in the calorimeter and measure the initial temperature of the water.

And again, that 50 centimetres cubed of water needs to be the same throughout the investigation.

That's another one of our control variables.

We're going to light the wick on the alcohol burner and when the water temperature has increased by 30 degrees Celsius, we will extinguish the flame.

It's important now that you remember to record the final temperature of the water because you'll have the initial temperature and the final temperature.

So we will be able to work out the temperature change of the water and also remember to record the final mass of the alcohol burner so that we can work out the amount of alcohol that has combusted.

You will then need to repeat this experiment using different alcohols in your alcohol burner so that we can then compare the data between different types of alcohol.

There are some important safety features that you need to consider when carrying out this experiment, so make sure you have completed your own risk assessment if you want to pause the video now, follow this method to collect your calorimetry data.

Then come back when you have finished the experiment and recorded all your data in the results table.

If you were unable to collect any calorie data, then there is a sample set of calorimetry results here.

You can see that we've used methanol, ethanol, and propanol as our three different alcohols in the alcohol burner.

We've recorded the initial mass and the final mass of the burner, and we have the initial temperature and final temperature of the water.

Well done for working hard in the first part of today's lesson.

We now have a set of calorimetry data.

We are going to move on to analyse our calorimetry data.

We can use calorimetry data to calculate the mass of alcohol needed to cause a one degree Celsius rise in temperature of the water.

And you can see our calorimetry data shown there below.

To calculate the mass of alcohol needed to cause a one degree Celsius rise in temperature of the water, this is what we need to do.

First of all, calculate the mass of alcohol that combusted.

So to do that, you need to take the initial mass of the burner and minus the final mass of the burner.

And working out that change between the initial mass and the final mass will tell you the mass of alcohol that combusted.

Secondly, we are going to calculate the temperature change of the water.

And to do this, we take the final temperature of the water.

So this time we're gonna start with the final temperature and we are going to minus the initial temperature.

And then for the third step, to calculate the mass per one degree celsius rise, we will take the mass of alcohol combusted and divide this by the temperature change of the water.

And this will tell us the mass of alcohol needed to cause a one degree Celsius rise in the temperature of the water.

Let's have a go at putting that into practise.

So calculate the mass of ethanol needed to cause a one degree Celsius rise.

Now, I'm gonna go through this one with you and then it'll be your turn to have a go.

So first of all, we're gonna work out the mass of ethanol that combusted.

To do that, we're gonna take the initial mass of the burner and we are gonna minus the final mass of the burner.

So that is 275.

20 grammes minus 274.

00 grammes.

And this gives us a mass of 1.

20 grammes.

So that's our mass of ethanol that combusted.

Now we can work out the temperature change.

So we can see the initial temperature is 20 degrees celsius and the final temperature is 50 degrees Celsius.

So to work out the temperature change, we do final take away initial temperature.

So we have 50 minus 20 degrees Celsius and this gives us a temperature change of 30 degrees Celsius.

We want to know the mass of ethanol needed to cause a one degree Celsius temperature rise.

So we will take that mass of ethanol, the 1.

20 grammes, and we are going to divide that by the 30 degrees Celsius temperature change.

And this gives us our final answer, which is 0.

040 grammes of ethanol needs to be combusted per degree Celsius.

So this means 0.

040 grammes is needed to cause a one degree Celsius temperature change.

If we wanted to know the mass that was needed to cause a 10 degree celsius change, we would take that answer there and times it by 10.

Your turn now.

Calculating the mass of methanol needed to cause a one degree Celsius rise.

So we're gonna split it into those three steps.

First of all, work out the mass of methanol combusted, then work out the temperature change of the water and then work out the mass of ethanol needed to cause a one degree Celsius temperature rise.

So if you pause the video now, have a go at answering that question and then come back when you're ready to go over the answers.

Well done for having a go at this multi-step calculation.

So to work out the mass of methanol that combusted, you should have done 276.

40 minus 275.

20 grammes.

And that means the mass of methanol combusted was 1.

20 grammes.

To work out the temperature change of the water, you do final temperature minus initial temperature.

So hopefully, you did 49 degrees Celsius minus 20 degrees Celsius gives us a temperature change of 29 degrees Celsius.

And to work out the mass of ethanol needed to cause a one degree Celsius temperature rise, we do the mass of methanol combusted divided by the temperature change.

So this will be 1.

20 grammes divided by 29 degrees Celsius, and that gives us an answer of 0.

041 grammes per degree Celsius.

Well done for having a go at that calculation and hopefully, you worked through it correctly and got the correct final answer.

It's time to have another go.

So this time, we're going to use our final set of data, which was on propanol.

So can you calculate the mass of propanol needed to cause a one degree Celsius rise? Again, complete this question in the same way, working out the mass of propanol that combusted, then the temperature change of the water and then see if you can get the final answer of the mass of ethanol needed to cause a one degree Celsius temperature rise.

Pause the video now and have a go at this question.

Okay, let's see how you got on.

The mass of propanol that combusted is 1.

10 grammes.

So we did the initial mass minus the final mass.

The temperature change of the water was 51 minus 20 and that gives us a final answer of 31 degrees Celsius and therefore, the mass of ethanol needed to cause a one degree Celsius temperature rise is the mass of propanol that combusted divided by that temperature change.

So 1.

10 grammes divided by 31 degrees Celsius and that gives us our answer of 0.

035 grammes per degree Celsius.

Well done if you got that one correct.

You're doing really well in today's lesson.

We can move on now to compare our data and when we compare the data, if a lower mass of alcohol is needed to cause the same temperature rise on the same volume of water, then this fuel is releasing more energy.

So let's have a look at our data and see what this means.

So on our data, 0.

040 grammes of ethanol causes a one degree Celsius rise and less than that, only 0.

035 grammes of propanol causes a one degree Celsius rise.

We need to combust a lower mass of propanol to cause a one degree Celsius rise in temperature of the same volume of water.

So therefore, the propanol releases more energy than the ethanol when it is combusted.

Time to check we've just understood that last point.

So using the data of the mass needed to cause a temperature rise, which alcohol releases the most energy when combusted? Is it methanol? And you need 0.

041 grammes of methanol to cause a one degree Celsius temperature rise.

Is it ethanol, which you need 0.

040 grammes to cause a one degree Celsius temperature rise? Or is it propanol? And you need 0.

035 grammes of propanol to cause a one degree Celsius temperature rise.

Well done if you choose option C, propanol.

This is the correct answer and this is because we use a lower mass of propanol.

So we only use 0.

035 grammes to cause a one degree Celsius temperature rise on the same volume of water.

Therefore, propanol is releasing more energy when it is combusted compared to methanol and ethanol.

We have another question to have a go at here.

Which alcohol releases the most energy when combusted? A, 0.

030 grammes of alcohol A is needed to produce a one degree Celsius rise in temperature.

Option B is 0.

035 grammes of alcohol B is needed to produce a one degree Celsius rise in temperature.

Or option C, which is 0.

040 grammes of alcohol C is needed to produce a one degree Celsius rise in temperature.

So which alcohol releases the most energy when combusted? The correct answer is option A.

So well done if you chose option A.

And this is because when you compare the three alcohols, alcohol A requires the lowest mass to be combusted to produce that one degree Celsius rise in temperature.

Therefore, alcohol A is releasing the most energy when combusted.

Time for us to move on to our final practise task of today's lesson.

And what you need to do here is carry on analysing that calorimetry data.

So question one, in an experiment, 1.

4 grammes of propanol produced a 45 degree Celsius rise in the temperature of 100 centimetres cubed of water.

And then we've got 1.

2 grammes of butanol.

So we've got a different alcohol here, and this produced a 46 degree Celsius rise in the temperature of 100 centimetres cubed of water.

So we've got a temperature rise on the same volume of water when we've used two different alcohols in here.

And first of all, what you need to do is calculate the mass of each alcohol that needs to be combusted to cause a one degree Celsius rise to the same volume of water.

And once you have worked that out for both of those alcohols, you can then have a go at B, which is which fuel releases the most energy when combusted? And you need to give a reason for your answer there.

If you pause the video now, have a go at answering question one, part A and part B, and then come back when you're ready to go over the answers.

Welcome back.

Let's see how you got on.

If we start with propanol, the mass of propanol, that combusted was 1.

4 grammes.

It said that in the question.

The temperature change of the water was 45 degrees Celsius.

Again, we were given that in the question.

So we needed to work out the mass of propanol needed to cause a one degree Celsius rise, and you do 1.

40 grammes divided by 45 degrees Celsius, and this gives you your answer of 0.

031 grammes per degree Celsius.

We then would need to do the same for the other alcohol there, which is butanol.

So we know the mass of butanol that combusted was 1.

2 grammes and we know the temperature change of the water was 46 degrees Celsius.

And we know both of these because they were given to us already in the question.

So to work out the mass of butanol needed to cause a one degree Celsius rise, we do 1.

20 grammes divided by 46 degrees Celsius and this gives us our answer of 0.

026 grammes of butanol needs to be combusted per one degree Celsius temperature rise of the water.

We've got the answers to A shown there and we can then move on to B and work out which fuel releases the most energy when combusted.

So the answer is butanol, and butanol releases the most energy when combusted.

We know this because less butanol was combusted to produce the same temperature rise on the same volume of water.

Well done if you got A correct and you calculated the mass of alcohol needed to be combusted to cause a one degree Celsius temperature rise.

And then well done again if you were able to use your answer to A to work out which fuel released the most energy when combusted.

For the final part of this practise task, we have got some samples of different alcohols that were burned to determine the mass of each alcohol needed to raise the temperature of 100 centimetres cubed of water by 15 degrees Celsius.

And what you need to do is look at this data and describe the trend in the data.

So we have got five different alcohols, methanol, ethanol, propanol, butanol, and pentanol.

You've been given their molecular formulas and you can see there the mass of alcohol that was burned to cause that temperature rise on the same volume of water.

So can you describe the trend in the data? Pause the video now, have a go at answering this question and then when you come back, we'll go over the answer.

We needed to describe the trend in the data.

As the number of carbon atoms in the alcohol increases, the mass of alcohol needed to be burned decreases.

The longer the carbon chain length of the alcohol, the more energy is released during combustion.

You might not have used the exact same wording, but hopefully you've got a similar answer.

You could always pause the video now and add any details that you missed to your answer if you need to.

We have reached the end of today's lesson on combustion of alcohols and we have collected our calorimetry data and then we have moved on to analyse our calorimetry data.

Well done.

You've worked really well in today's lesson.

Let's just summarise some of the key learning points from today's lesson.

Calorimetry can be used to measure a reaction's energy change indirectly.

Calorimetry data can be used to calculate the mass of alcohol needed to cause a one degree Celsius rise in the temperature of the water.

An alcohol that causes a one degree Celsius temperature rise when the least amount of alcohol is combusted is releasing the most energy.

The energy change of combustion for a variety of alcohols can be compared to the molecular formula of each alcohol.

I really enjoyed today's lesson.

I hope that you have too and I hope that you're able to join me for another lesson soon.