Hello, everyone.

It's lovely to be learning science with you today.

I'm Dr.

Pemberton, and I'm really looking forward to working through the lesson with you.

So let's get going.

Today's lesson is about finding the strongest magnet.

You are going to use the knowledge you already have about how magnets work, and you'll also improve your practical skills by working as a scientist.

The learning outcome today is that you can explore the strength of different magnets and find fair ways to compare them.

It's part of our big question, how do forces make things happen? I'm looking forward to working as a scientist with you, and I'm excited about exploring magnets again.

I hope you are too.

These are the keywords that we'll be using in today's lesson.

Strength, magnetic force, material, distance, and compare.

Some of these words are new today, but some of them should be familiar to you already.

Here are the explanations showing what each of the keywords means.

I'll explain these words as we come across each of them during the lesson, so we won't spend time going through each one now.

It's just here as a reminder and you might like to come back to it later to check that you are confident using each of those keywords.

Here's our lesson outline for today.

There are three parts to our lesson.

We'll begin by learning that magnets can be different strengths.

Then we'll learn how scientists ask questions and plan investigations, and finally, we'll think about how and why scientists compare their results.

We're going to get going on the first part of our lesson, beginning with magnets can be different strengths.

Magnets can vary in strength.

Stronger magnets create stronger magnetic force.

You see here that we have two magnets.

The top one is a weak magnet, so it only creates a weak pull on these stainless steel scissors.

The second magnet is stronger.

The longer arrows represent the fact that this stronger magnet creates a stronger magnetic pull.

The strength of a magnet can depend on many different things.

Well, the material a magnet is made from is one thing that can affect its strength.

The thing is you can't tell how strong a magnet is by looking at its size or shape.

In fact, some small magnets are stronger than large magnets, which is a bit of a surprise.

There are different ways that we can describe a magnet's strength.

It could be described by how much pulling force it has.

If we're describing it that way, then we can say that the stronger the magnet, the greater the amount of material it can attract.

So, in this example, we can see that a weak bar magnet has attracted three iron nails, but in this example, the strong bar magnet has attracted seven iron nails.

The distance over which a magnet can attract an object is also a result of its strength.

If we are describing strength this way, then we can say that the stronger the magnet, the greater the distance its pull force can be felt and seen.

Let's look at an example to help with this one.

In the first picture, we can see a weak magnet attracting an iron nail from 10 millimetres away.

However, this stronger magnet can attract the iron nail from 15 millimetres away.

We know that the second magnet is stronger because it can attract nails from further away.

Let's check what we've learned so far by trying these questions.

Firstly, which word could fill the gap here? Magnets create stronger magnetic forces.

That's right.

Stronger magnets create stronger magnetic forces.

Let's try another one.

Is this true or false? Bigger magnets are always stronger than smaller magnets.

What do you think? That's correct.

This is false, but why do you think it's false? Do you think it's because a, the strength of the magnet depends on its size, or b, because the strength of the magnet can depend on the material it's made from? Well done.

We talked about this one earlier.

It's b, the strength of a magnet can depend on the material it's made from.

You can't tell how strong it is from its size.

Now it's your turn to do some science.

This is your first challenge of the day.

Here we can see that Aisha and Alex are discussing magnets.

Aisha says, "A stronger magnet will be able to pick up more nails," but Alex says, "A stronger magnet will be able to attract a nail from further away." Who do you agree with and why? Pause the video here to discuss your ideas with a partner.

When you're ready, come back and we'll look at the answers together.

How did you get on? Well, both Aisha and Alex are correct.

A stronger magnet will pick on more nails and it will also attract a nail from a distance further away.

Let's move on to the second part of our learning today, where we are going to consider how and why scientists ask questions and plan investigations.

Ah, here's Jacob.

Jacob asked a question to compare different types of kitchen roll.

He asks, "Which type of kitchen roll soaks up most water?" Hmm.

Now, if Jacob wants to investigate this like a scientist, there are lots of things that could be changed each time he does the investigation.

What are they? Do you have any ideas? Jacob plans to test and compare the type of kitchen roll in a fair way.

There are some things which he can control.

Jacob could change the size of the rectangle of kitchen roll.

It's important to make sure they're all the same.

He can control where he does the investigation, because it wouldn't be fair if he did one in a really hot, dry room and one outside in the rain.

He can also control the amount of time that he dips the kitchen roll into water, and finally Jacob can control the amount of water he tries to soak up.

There are some things that Jacob cannot control, such as the thickness of the kitchen roll, because different types are different thicknesses, and he can't change that.

He just has to use the thickness they come in from the shops.

Because he can't control everything, we are not calling it a fair test because we can't make everything the same.

However, we still want to be fair about all the things we can control because we're scientists.

So let's go back to magnets.

Jacob is comparing kitchen roll, but we can ask questions to compare the strengths of magnets.

When we are changing the type of magnet, there are some things we can't control, such as the length of the magnet, or the thickness of the magnet, but we still want to do everything we can to compare them in a fair way.

Let's think about what your question could be if you want to compare magnets.

Well, your question could be which magnet is strongest? It could be, which magnet can hold the most magnetic objects, or perhaps, which magnet can attract things from furthest away? I wonder if you can think of any other questions.

Right, let's see what we can remember so far.

Why do scientists carry out investigations? Is it a, to use interesting equipment, b, to work with other scientists, or c, to answer questions? Have a think.

Yes, that's correct.

Scientists carry out investigations to answer questions.

Let's try another one.

Which of these questions could be answered using a fair test investigation? Is it a, which magnet is heaviest, b, which magnet is nicest, c, which magnet is my favourite, d, which magnet is strongest? I'll give you a few seconds.

Correct.

You can answer two of these questions with a fair test investigation, a, which magnet is heaviest, and b, which magnet is strongest? The other two questions could not be investigated scientifically because you can't make observations or take measurements.

Now it's your turn again.

You need to plan an investigation to compare two magnets and to answer your question, which could be about the number of objects, or about the distance.

Jacob's question is, "Which magnet can hold the most objects?" That's a good question, and there's lots of things you need to think about.

Firstly, what equipment will you need? Secondly, what will you measure that will allow you to answer the question? To plan your investigation, you need to draw a labelled diagram and add notes to say what you'll do.

Pause the video and come back when you've made a plan.

Hello.

How did you get on? You might have thought of something like this.

If you asked which magnet can attract things from furthest away, your plan might look like this.

Here, you can see from the drawing that the plan is to put a paperclip at one end of a ruler next to the zero mark and gradually move the bar magnet towards it.

Let's read the notes.

We will put a paperclip at one end of a ruler and we'll move the magnet closer along the ruler until it attracts the paperclip.

We will measure the distance it attracts the paperclip.

We will start with the bar magnet and then swap it for the horseshoe magnet to compare magnet strength.

That's great.

However, you might not have chosen to investigate distance.

If you decided to compare the number of items magnets could hold to measure strength, your diagram and notes might have looked like this.

In the diagram, you can see that they plan to use a bar magnet to attract paperclips, and the notes say, we will count how many paperclips each magnet can hold in the air without dropping them.

We'll start with the bar magnet and then swap it for the horseshoe magnet to compare magnet strength.

Great, the plan is clear and the diagram is too.

Now we've reached our final cycle for today.

We are going to look at how scientists compare their results.

When scientists carry out investigations, they record their results.

Now, results come in different forms. Their results might be descriptions of things they have seen or their results might be measurements they have made.

But why do scientists record results? What's the point of it? Well, there's a number of reasons.

Scientists record their results so they don't forget what they have found out.

They also record them so they can compare them with the results of other investigations.

Scientists might compare their results with their own results from other investigations, or they might compare them with someone else's results, but why would you do that? Why might you compare your results with those from other investigations? Well, there are lots of reasons that scientists compare the results.

We can see two scientists here doing so.

I wonder why they are doing it.

It could be because it helps 'em check whether the results are likely to be true.

It helps 'em find patterns in their data, and it helps them understand what happens if you change something in an investigation.

Let's take a minute checking again to see what we can remember.

Is this true or false? It's important for scientists to record results.

Yes, it's definitely important for scientists to record their results, but why do you think that? Is it because a, if you do another similar investigation later, it's important to be able to compare the results of the two different investigations, or is it b, because when you write up the investigation, it will be incomplete without a results section? That's right, it's a, scientists record their results, because if they do another similar investigation later, it's useful to be able to compare the results of the two different investigations.

Let's try another one.

This one's multiple-choice.

Which of these are reasons that scientists compare their results with those from other investigations? Is it a, because it's good for scientists to make time to talk to each other? Is it b, because it helps them check whether their results are true, or is it c, because it helps them find patterns? Great, it's two of the reasons.

Scientists compare their results with those from other investigations because it helps them check whether they're true and because it helps them find patterns in data.

Now it's time for your final task of the lesson.

You are going to carry out the investigation that you planned in task B and you need to record your results.

You might like to record your results in a table like this.

You can see that there are two columns.

On the left hand side are the magnet types, and on the right hand side is a column in which to record the number of paperclips attracted and held by the magnet, or if you've done the distance one, it might be the distance that the paperclip can be attracted from.

In this table, the pupil is planning to test three magnets, a large bar magnet, a small bar magnet, and a horseshoe magnet.

I wonder which magnets you will compare.

When you've carried out your test, your next step is to compare your results with another group.

When you do this, there are two things you need to do.

When you've carried out your test, your next step is to compare your results with those of another group.

When you do this, there are a few things you need to do.

You'll need to explain what you did so the other group understands how you got those results.

You'll need to show them your results and give them time to look at them, and you'll need to tell them what your results suggest about which magnet is strongest.

When both groups have done this, you need to think about these questions.

Was their investigation the same or different to yours, and do their results show the same thing? If they don't, why do you think this is? Remember that in science, if you don't all have the same results, it doesn't necessarily mean that someone has done something wrong.

It can just mean that your investigations show different things or measure different things.

Now, pause the video and carry out your work.

Welcome back.

How did you get on? Let's have a look at the sorts of results you might have got.

If you decided to measure the strength of a magnet by the distance it could attract a paperclip, your results may look like this.

You can see that the bar magnet, the small bar magnet, attracted the paperclip from 24 millimetres away.

The large bar magnet attracted it from 15 millimetres away, and the horseshoe magnet attracted the paperclip from 19 millimetres away.

However, perhaps you decided to measure the strength by the number of paperclips it could hold, and your results might look more like this.

Here we can see that the smaller bar magnet attracted and held 35 paperclips compared to 26 for the large bar magnet and 28 for the horseshoe magnet.

So those two groups measured different things, but how did their results compare? How did your results compare with those of another group? Aisha is describing what her results show, and she says, "I measured the distance different magnets could attract a paperclip.

I found that the small bar magnet was strongest." Alex says, "I compared the number of paperclips different magnets could hold.

I found that the small bar magnet was the strongest." Oh, that's interesting.

Aisha and Alex measured the strength in different ways, but both of their results showed that the small bar magnet was strongest.

Finally, I want to have a quick look at some more results with you.

Here are the results from two different groups.

They both measured strength by the distance a magnet could attract a paperclip.

Do they show the same thing? Take a minute to pause the video and look at the results and compare them.

Yes, they do show the same thing.

Both results suggests that the small bar magnet is strongest and the large bar magnet is weakest.

But you can see that both sets of data show slightly different numbers, and this is one of the reasons why scientists repeat their tests many times just to check that they're getting reliable measurements.

Well, well done.

We've come to the end of our lesson.

So let's look back over our learning from today with a summary.

Magnets can vary in strength.

Stronger magnets create stronger magnetic force.

The strength of a magnet depends on many things, including the material it's made from.

Scientists can use investigations to compare magnets.

Scientists compare their results with other investigations that have been carried out.

Thank you for joining me this lesson.

It's been great fun investigating magnets together.

You've learned more about magnets and you've practised your skills as a scientist.

Well done for your hard work and have a great day.

See you next time.