Hello there, I'm Mr. Forbes, and welcome to this lesson from the Energy of Moving Particles unit.

This lesson's called measuring specific heat capacity, and in it we'll look at two different ways of measuring the specific heat capacity.

By the end of this lesson, you going to have carried out two experiments in measuring specific heat capacity.

One, to measure the specific heat capacity of a liquid, like water, and another to measure the specific heat capacity of a metal sample.

Here are the keywords and phrases that will help you in this lesson.

The first is specific heat capacity, and that's the change in internal energy when the temperature of one kilogrammes of material changes by one degree Celsius.

The next is an immersion heater.

And an immersion heater is an electrical device that we can use to heat a liquid by submerging the heater in it.

The next is joulemeter, and that's a metre that measures the energy transferred by an electric current.

And finally conservation of energy.

And that's the principle that states that the total amount of energy is the same before and after any energy transfer.

You can return to this slide at any point in the lesson.

The lesson's in two parts, and in the first part we're going to be looking at a way of measuring the specific heat capacity of a liquid sample using an immersion heater.

And in the second part we're going to look at a way of measuring the specific heat capacity of a metal sample by submerging that in water and transferring energy.

So let's start by looking at the immersion heater method.

So in our first experiment we're going to measure the specific heat capacity of water using an immersion heater.

And an immersion heater is a small electrical heating element that we can place in a liquid.

So if we're going to be using a liquid, we'll need to contain that liquid in something like a beaker.

So we put the water in the beaker, and then we can place an immersion heater into it.

And that immersion heater is connected to a low voltage power supply.

Low voltage power supply will provide an electric current to the immersion heater.

And we use a low voltage supply to reduce the risk of electrocution.

You could get a shock if we used a higher voltage one.

So we're going to pass a current to that heater, and that's going to become hot.

And that heater then is going to transfer energy to the water.

We'll need to know how much energy is actually transferred to the water.

And for that we're going to use a joulemeter.

And a joulemeter is just a device that we can put in a circuit and it measures the current and the voltage, and it uses that to calculate the energy transferred through that metre.

So we're going to take a metre, something like this, and we're going to connect it into the circuit so the current passes through the metre.

That means we connect it between the power supply and the immersion heater.

And when we turn the circuit on, the reading on that metre is going to increase, and that's going to show us the energy transferred to the heater in that circuit.

So let's imagine we've connected a metre to the circuit and we've got the readings at the start time and the end time.

What I'd like you to do is to calculate how much energy has been transferred through that joulemeter to the immersion heater.

So pause the video, work that out, and restart please.

Welcome back.

Hopefully you selected 1,215.

7 joules.

And you can find that by looking at the difference in the readings on the metre.

So we take the start reading of energy away from the end reading, something like this, and that gives us the answer.

So, well done if you selected B.

To measure the mass of the water we can use a top pan balance.

So we are going to place an empty beaker on top of the balance and record what the mass of that beaker is, and then we put water into the beaker, something like this, and we can then record the amount of mass there is there.

And to find the mass of water, all we need to do is to find the change in mass.

How much has that mass gone up by? So we can find the mass of water by subtracting that initial empty beaker mass from the full beaker mass.

And that gives us 203.

3 grammes.

Okay, let's see if you can do that.

I've got a beaker placed on a balance, and then I put water in.

And you can see the two readings there.

What's the mass of water in that beaker? Pause the video, work that out.

Welcome back.

Hopefully you selected Option B 203.

1 grammes.

That's the difference of the change in readings if we subtract the empty beaker mass from the full beaker mass.

So, well done if you've got that.

So our process is like this.

We're going to have a known mass of water, and we're going to heat it, and we're going to record the start temperature, the end temperature, and the energy provided to that water in a table that looks something like this.

Now as you can see, I've got the start and end temperatures, but I actually need to know the change in temperature for each of the example masses of water.

So what I do is I'm going to find that by subtracting the start temperature from the end temperature for each of the different samples.

So for the first one, we subtract the values, it's 13.

7 degrees Celsius, and we can do that process for each of the different masses of water.

And we get these values here.

Once we know those temperature changes, we can calculate the specific heat capacity.

And we can calculate it using a rearranged version of the equation that you may have seen in an earlier lesson.

The specific heat capacity is going to be the energy supplied to the sample, divided by the mass times the temperature change, as shown there.

So we can do that for the first row here.

We've got a mas of water of 0.

20 kilogrammes, and we've got a temperature change of 13.

7 degrees, and we've got an energy supply of 12,300 joules.

And so we can calculate the specific heat capacity using that data, and that gives us a specific heat capacity of 4,489 joules per kilogramme per degree Celsius.

And I can fill that in the table there.

And then I can repeat that calculation for each of the other rows at the table giving me a range of values that are all very similar.

Okay, I'd like you to calculate specific heat capacity, and in this example I've got a different liquid.

I've not got water.

So I'd like you to use the data in the table to calculate its specific heat capacity, please.

Pause video, do that, and restart.

Welcome back.

Hopefully you selected option D.

And the mathematics is shown there in a slightly different format where I've got the energy and divided it by the mass times the temperature change.

So, well done if you chose option D.

Now we're going to actually carry out this experiment three times so that we can find a mean value, to try and get a better specific heat capacity answer.

So to find the mean value, what we do is we add the three values and divide by three.

So I've got three specific heat capacities here, all slightly different.

We're gonna add those three together and divide by three to give us a final answer for our specific heat capacity.

And so I've done that and that gives me a final answer of 4,345 joules per kilogramme per degree Celsius.

Okay, here's another experiment.

And in this one we've carried out five experiments and found specific heat capacities.

I'd like you to find the mean value of this for me please.

So pause the video and do that.

Welcome back.

Hopefully you selected A.

To find the mean value we add all five of those together and then divide by five because there were four examples, and that gives us 2,800 joules per kilogramme per degrees Celsius.

Well done if you got that.

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

What I'd like you to do is to follow this set of instructions here.

We're gonna connect the immersion heater to a joulemeter and a power supply, put some water into a beaker, we're going to heat that up while there's a thermometer in it, and we're gonna put a lid on the top to stop energy losses to the surroundings.

We need to record the starting temperature, and heat that liquid for five minutes, then turn everything off, record the end temperature, and the energy supplied using the values from the joulemeter.

And then, once that's been carried out, repeat those processes with 250 grammes and 300 grammes of water.

As we carry out the experiment, we record all the results in a table like the one shown here.

Once you've got all that data, you can calculate the specific heat capacities for each of the three different samples.

And finally, once we've got those three values, we can find a mean value, and that'll give us our best estimate of the specific heat capacity of water.

So pause the video, follow all these instructions, complete the data table, and then restart when you're done, please.

Welcome back.

Hopefully you've got a set of results something like this.

I've got my final specific heat capacity of 4,345 joules per kilogramme per degree Celsius.

The actual value for water is 4,200, but this experiment tends to give a value that's a little bit higher than that.

So, well done if you've got anything close to that.

And now it's time for the second part of the lesson, and we're gonna carry out another experiment into measuring specific heat capacity.

But this method doesn't require any electrical heating.

We're going to be warming some metal samples and placing them into cooler water, and using the temperature change of that water in order to calculate the specific heat capacity of the metal samples.

Let's start that.

As I've said, we're going to try an alternative method for measuring the specific heat capacity of some metal samples.

And this process usually works quite a bit better than the earlier one.

It gives more precise results.

So what we're going to do is we're going to heat up a sample of metal to a known temperature, and then we're gonna replace it inside a container of water.

And what's going to happen is that hot metal is placed in the water, and it's going to warm the water up.

The metal will cool down and the water will warm up as that happens.

And after a few minutes the metal and the water will reach the same temperature.

We are going to do that inside an insulated container because what I want to do is to ensure that all the water, sorry, all the energy from the metal is transferred to the water and not lost to the surroundings.

So I need an insulated container to reduce that energy loss.

Let's see if you can work out which type of container to use.

Which container will minimise energy losses to the surroundings by conduction? Is it a glass beaker, polystyrene cup, or a steel can? Pause the video and work it out.

Welcome back.

Hopefully you selected B.

The polystyrene cup is the poorest conductor, is the best thermal insulator.

So that'll work best in our experiment.

Some sort of expanded polystyrene.

This method relies on the principle of conservation energy, and that tells us that the energy gained by the water is going to be equal to the energy lost by the metal.

So when I've got a container like this, the energy transferred to the water can be found by looking at its mass, its specific heat capacity, and its temperature change.

And the value for the specific heat capacity of the water is well known.

So we're gonna use that value in our calculations.

We can measure the temperature change with a thermometer.

And we can measure the mass of water that we put in there.

The value for the energy that's gained by the water is going to be exactly the same as the energy lost by the metal as it cooled down inside the water.

So we need to be able to calculate the energy change of the water.

So I've got an example question here.

The specific heat capacity water is 4,200 joules per kilogramme per degree Celsius.

The temperature of our 0.

1 kilogramme sample of water increases by 8 degrees Celsius.

Calculate the energy change for the water.

So I'd like you to work out what that energy change for the water is.

Pause the video, work it out, and restart please.

Welcome back.

Hopefully you selected option C, 3,360 joules.

And we do that by using the energy and specific heat capacity equation, which is written there.

And that gives us an energy of 3,360 joules.

Well done if you've got that.

So if we know the mass and the initial temperature of a metal sample we can find its specific heat capacity, and we can use an equation that we've seen earlier in the lesson.

The specific heat capacity is going to be the energy lost by the metal divided by its mass and temperature change.

You can find the mass of the metal sample by just placing it on a balance.

And we put it on a balance when it's dry before we carry out the experiment and note that down, 'cause we don't want to be weighing our sort of wet piece of metal later on.

So I'm going to record the mass of the sample.

We have to heat up that metal block in order for it to be able to heat up the water.

And to do that we need to heat it to a known temperature.

And there's a couple of ways of doing that.

The first is probably the simplest, we can place it in a hot water bath.

A water bath is a controlled bath of water at a very specific temperature that you set on a dial at front.

So we can fill that bath like that with water, and that will be heated to a set temperature.

And we can adjust it to say 60 or 80 degrees Celsius and place the metal block inside there for it to warm up.

If we don't have a water bath, we can do something similar with boiling water.

So we can get a beaker, heat it perhaps with a Bunsen or something like that, and we can carefully place the metal in the hot water and allow it to reach a 100 degrees Celsius, 'cause the water's boiling.

In either example, we need to place the block of metal into there for several minutes until it's reached the same temperature as the water.

It's reached thermal equilibrium.

As part of this experiment, we're going to be calculating the temperature change of the block of metal.

So I've got a block of metal, it's got a temperature of 90 degrees Celsius, and it's placed in water which is at 20 degrees Celsius.

The water temperature increases to 26 degrees Celsius.

What's the temperature change for the metal? So pause the video, work that out, and restart please.

Welcome back.

Hopefully you selected B.

What's happened here is that the temperature change is the final temperature minus the initial temperature, and the metal block, because it's in the water, has reached the same temperature as water, which rose to 26 degrees Celsius.

So the block started at 90 and finished at 26 degrees.

So its temperature is decreased by 64 degrees Celsius.

So the temperature change is minus 64 degrees Celsius.

Well done if you got that.

Okay, before we carry out the experiment, we're going to try an example calculation.

I've got a metal block, and it's got a mass of 0.

090 kilogrammes, and it's cooled by 35.

3 degrees Celsius when placed in water.

The energy gained by the water by heating is 1,500 joules.

Calculate the specific heat capacity of the metal.

So to do that I need to realise that the energy gained by the water is equal to the energy lost by the metal.

That allows me to calculate the specific heat capacity like this.

Specific heat capacity is energy lost by the metal divided by mass times temperature change.

The energy lost by of metal was 1,500 joules.

The mass was 0.

090 kilogrammes, and the temperature change was 35.

3 degrees Celsius.

So that will give me a specific heat capacity of 472 joules per kilogramme per degree Celsius.

Let's see if you can perform the same sort of calculation with the data here.

I'd like you to read through that information, pause the video, and use it to calculate the specific heat capacity of the metal, and then restart when you're done.

Welcome back.

Hopefully you selected the bottom option, 654 joules per kilogramme per degree Celsius.

And the maths is shown here.

We've got the equation, we've filled in the values taken from the question, and found that specific heat capacity.

and that's 654.

So, well done if you got that.

Okay, now it's time for you to carry out the experiment to find the specific heat capacity of some metal samples.

And the instructions are shown here.

We're gonna measure the mass of of small sample of metal and record it.

We're gonna place that sample into a hot water bath so it reaches a known high temperature.

While it's doing that, we measure out 0.

1 kilogrammes of cold water into a well insulated container.

We record the starting temperature of that water, then we use a pair of tongs to very carefully take the hot metal from the hot water and place it into the cold water.

We then stir gently for a few minutes using the thermometer, and record the maximum temperature that that water will reach.

As we're carrying out the experiment, we record the results for each different sample we use in a table like this.

So this is for metal A.

And I record the mass of the water and mass of the metal, the start and end temperatures of both, and the change in temperatures.

We calculate and energy change and specific heat capacity.

We calculate the energy change of water using the data for the water.

So we've got energy changes, mass of the water, times specific heat capacity for the water, times the temperature change for the water.

We then realise that the energy change for the metal is the same as the energy change for the water, and we can calculate the specific heat capacity of the metal using the equation shown there.

So pause the video, work through all of those steps, and try and find the specific heat capacity of some samples of metals.

Welcome back.

And here's some examples I've carried out.

I've found the specific heat capacity of two different metals, and they're 542 joules per kilogramme per degree Celsius for metal A, and 255 for metal B.

Obviously your metal samples would've been different than mine and you'll get different values, but well done if you've got some answers.

Okay, we've reached the end the lesson, and this is what we've covered today.

We can find the specific heat capacity of some materials in two different ways.

We can heat a sample with an electric current, measuring the energy provided to it directly, and using that value to calculate the specific heat capacity.

And that works well with liquids where we can place an immersion heater in, and it can work well with some solids as well if we can place that immersion heater inside the solid.

The second method we can use, we can heat a sample of a material to a high temperature, and then place it into water, and then we can use the temperature change of the water to calculate a specific heat capacity of the substance.

Well done for reaching the end of the lesson.

I'll see you in the next one.