Lesson video

Hello, everyone.

How are you doing today?

I hope you're feeling really good.

My name is Ms. Afsal and I will be a science teacher for this lesson.

I'm feeling so good about that because I'm really into this subject.

We are looking at rocks.

What's not to love about rocks?

And today in particular, we are be exploring the hardness of different rocks.

We'll be taking inspiration from someone called Friedrich Mohs.

So today's lesson is called Moses's Scale of Hardness.

That's what we'll be exploring and investigating.

And hey, maybe we'll be creating some scales of our own.

I hope you're feeling interested in this, excited about it.

I certainly am.

So if you're feeling ready with some energy, some focus and some enthusiasm, we'll begin our lesson now.

The outcome for today's lesson is I can learn more about the hardness of rocks from the work of important scientists.

That sounds interesting to you.

We have some keywords in Alison.

Let's go through them one at a time.

My turn.

Your turn.

Rock, geologist, hardness, mineral, scale.

It's great to hear those keywords loud and clear.

I'll just repeat them one more time.

We have rock, geologist, hardness, mineral, and scale.

Pause here and share with someone which of these keywords have you heard of before?

Thanks for sharing.

And now let's find out what each of these keywords mean.

Rock is a solid material that occurs naturally in earth.

A geologist is someone who studies what the earth is made of.

Hardness is the quality of being difficult to bend, cut, or break.

A mineral occurs naturally and can be dug outta the ground.

A scale is a set of numbers or amounts used to measure or compare the level of something.

So these are our keywords.

Let's look out for them.

Let's listen carefully for them.

Let's think about these words.

They'll be coming up in our lesson today.

Our lesson is called Mohs' scale of hardness, and it has two learning cycles.

Scientists help us to learn about rocks and developing a scale of hardness.

Let's begin by exploring how scientists help us to learn about rocks.

Scientists called geologists study what earth is made of.

They help us to learn and understand more about rocks.

We can see some of our keywords there: geologists and rocks.

Geologists carry out investigations to compare and group different rocks on the basis of their physical properties.

And we can see some geologists with their hammers, with their tools on the screen there.

Perhaps they're at the site of a dig.

There are lots of ways to observe and measure the physical properties of different rocks.

We can scratch the surface of rocks to find out their hardness.

Another one of our keywords.

We can use the results of our test to decide which rocks to use for different purposes.

And we can see that there is someone having carried out a scratch test on some limestone.

What's here and share with someone.

What do you notice in that image where the limestone has been scratched with a nail?

Thanks for sharing what you noticed, your observations.

We'll be getting more into the scratch test a little later on.

Geologists investigate rocks in lots of different places.

Here's a geologist investigating volcanic rock.

Here's a geologist investigating rocks in a cave.

And here's a geologist investigating rock in a glacial lake.

Who's here and share with someone, imagine if you were a geologist, where would you like to be investigating rocks?

Would you like to investigate volcanic rock, rocks in a cave, or rocks in a glacial lake?

Thanks for sharing.

I think I'd like to investigate rocks in a cave.

It looks very mysterious and exciting.

Let's have a check for understanding.

What does a geologist study?

Is it A, what the earth is made of?

B, what the sky is made of?

Or C, what the oceans are made of?

Pause here and share with someone nearby.

What does a geologist study?

Well done if you selected answer A Indeed, a geologist studies what the earth is made of.

Let's have another check of our understanding.

Which of these careers could help us find out more about rocks?

Is it A, being a pilot, B, being a firefighter, or C, being a geologist?

Who's aim share with someone, which will help us find out more about rocks.

Thanks for sharing.

Well done, and well done if you chose answer C, indeed, the career of a geologist would help us find out more about rocks.

Jacob is investigating like a geologist.

He has scratched the surface of different rocks with a nail to test their hardness.

He has found that marble and gneiss are hard, and that sandstone, limestone, and chalk are not hard.

I wonder if that's what you would've guessed.

The problem I had using sorting circles was the rocks range from very hard, to quite hard, to not hard.

I can see that's quite a problem.

It's a bit simplified really, to sort them into simply hard and not hard.

Do you have any ideas to help Jacob?

What could he do to sort them more accurately from very hard to quite hard to not hard?

What's here and share with someone your ideas.

Thanks for sharing.

And now it's time for your first task.

I would like you to present the information from your own or Jacob scratch test investigation to show the order of results, rather than hard or not hard in sorting circles.

So you've done your rock scratch test, and you need to show how some rocks can be in between hard and not hard, therefore, not in a definite group.

So if you'd like to work with the results from Jacob's scratch test investigation, here they are.

There's the limestone.

You can see how it was scratched with a nail.

And can you see anything that may have been scratched off of the limestone, if you look closely?

There's the marble next.

Again, take a look.

Is there anything that's been scratched away?

There's the sandstone.

What can you see has been scratched or scratched away there?

There's the nice, what are you noticing?

And finally, there's the chalk, which has been scratched with the nail.

What do you notice?

Is there anything that has come away, has been scratched away from the chalk?

So take a good look at these results from Jacob's scratch test investigation, and then show the order of the results, rather than simply putting them in two categories of hard and not hard.

Enjoy your task, think carefully about it, and I'll see you when you're finished.

It's great to be back with you.

How did you get on with presenting your information from a scratch test investigation to show the order of results?

Jacob's wondering, is your scale similar or different to mine?

So we can see if we look at these images that we have got chalk is at the end of most soft and then we've got this arrow taking us all the way to most hard.

And then Jacob has placed each stone somewhere on this line, or we could call it a continuum.

So first we've got chalk, most soft, next was sandstone, then we had limestone, then marble, and finally nice was at the most hard end.

And let's hear some feedback.

So the chalk crumbled.

Sandstone showed a deep scratch, limestone showed some scratch, and some crumbling.

Marble showed a slight scratch, and gneiss showed no scratch.

Who's here and share with someone.

Is your scale similar to this one here or is it different?

Thanks for sharing everyone, and well done for having a go at this task.

And now we're onto our next learning cycle: developing a scale of hardness.

Friedrich Mohs was born in Germany in 1773.

He was extremely interested in rocks and what they could be used for.

A bit like us.

In 1801, he started to study the different physical properties of the rocks in his collection.

He wanted to use this information to organize rocks into groups because no one had done this before.

There we can see an image of Friedrich Mohs.

Let's have a check for understanding.

Friedrich Mohs was a famous scientist from the past who helped us learn about which of these things?

Was it A, plants, B, rocks, or C, animals?

We'll say it while you decide.

Well done if you selected answer B.

Indeed, Friedrich Mohs was a famous scientist from the past who helped us to learn about rocks.

Mr. Mohs knew that rocks were made up of different materials called minerals.

He observed that some minerals are very soft, and others are extremely hard.

He developed a set of numbers called a scale to compare hardness by how easily different minerals could be scratched using different objects.

I can see in that image there that rocks are made from minerals.

Mohs's scale is a list of minerals, a range from the softest number, one, to the hardest, number 10.

He found that talc is the softest as it can be scratched by all other materials.

And Mohs scale showed that diamond is the hardest.

Although scientists today have found several minerals to be harder than diamond.

Let's have a check for understanding.

Which of these things did Friedrich Mohs help us to learn about through his investigations?

Was it A, how volcanoes are formed?

B, the shape of the earth?

Or C, the properties of rocks?

Pause here and share with someone.

Which of these did Friedrich Mohs help us to learn about through his investigations?

Well done if you selected answer C.

Indeed, Friedrich Mohs helped us to learn about rocks and the properties of rocks.

Geologists continue to learn about the physical properties and uses of rocks.

They compare the results of their investigations to what Mr. Mohs did, and found out.

Mr. Mohs' scale is still very useful.

It helps us to determine the hardness of other rocks, decide what different rocks can be used for, and identify an unknown rock.

How exciting.

Let's have a check for understanding, true or false.

The results of a scientific investigation can be compared to other investigations that have already been carried out.

What's here and decide, is this statement true or false?

Well done if you selected true.

Indeed, the results of a scientific investigation can be compared to other investigations that have already been carried out.

And now I'd like you to justify your answer by choosing between one of these two statements.

Geologists today compare their investigations with the findings of scientists like Mohs to see if they have discovered anything new.

Or geologists today compare their investigations with the findings of scientists like Mohs as they are lazy.

What is there to decide?

Which of these two justifier your earlier answer?

Well done if you chose answer A.

Indeed, geologists today compare their investigations with the findings of scientists like Mohs to see if they've discovered anything new.

Not because they're lazy.

And now we've come to the time for your next task.

I would like you to try a Mohs test using different objects to scratch and compare the rocks in your collection.

Use this information to help you.

So hardness of nine, rock can be scratched with the tip of a steel nail file.

Hardness of three, rock can be scratched with the edge of a 1P coin.

Hardness of 2.

5, rock can be scratched with a fingernail.

So these are the three things that you will use to scratch at the rock.

The steel nail file, which gives a hardness of nine, a coin, 1P coin, which gives a hardness of three, and your own fingernail, which gives a hardness of 2.

5.

So pause here while you carry out your own Mohs test with these three objects to scratch and compare the rocks in your collection.

Enjoy your task, enjoy your most test, and I'll see you when you're finished.

It's great to be back with you.

So how did you get on with that task of using different objects to scratch and compare rocks?

Here's Aisha.

"I found that chalk could be scratched very easily with my fingernail, so I rated it at one on my scale.

I could scratch granite a bit with a nail file, so I rated it at nine on my scale.

" And here's Andeep.

"I found that some rocks could not be scratched with a coin, but they could be scratched with a nail file, so they must have a hardness rating somewhere between three and nine.

" Perhaps you had experiences like these, or maybe something different.

And now onto the next part of our task.

I would like you to present the findings from your scratch test to show the range of results using a scale.

Your scale could range from one to 10, or it might be different.

You could use your own surname for the name of your scale, similar to what Friedrich Mohs did.

You are after all geologists now, so you could be naming your own scales.

Pause here while you have a go at this task.

And I look forward to seeing the presentation of the findings from your scratch test using your scale when you finished.

It is great to be back with you.

So how did you get on with this task?

How did you get on with creating your own Mohs scale?

Or perhaps it has your name on the scale for rocks that you've tested.

Let's hear some reflections.

After testing my rocks using a 1P coin, a steel nail file, and my fingernail, I ordered them from softest to hardest.

And we can see there, we've got softest on the left and what looks like chalk.

And then we go all the way across to hardest on the right, and that looks like granite there on the right.

And all of these nine rocks have been placed against the number on the scale.

Let's hear some more.

Then I added a scale which showed the softest rock chalk as number one, and the hardest rock granite as number nine.

I name the scale with my own surname.

How wonderful.

In our lesson, Mohs's scale of hardness, we've covered the following: geologists study what the Earth is made of and help us to understand more about rocks.

Scientists from the past today and in the future help us to learn about the physical properties and uses of rocks.

The results of a scientific investigation can be compared to other investigations that have already been carried out.

Well done everyone for joining in with this lesson on Moses' scale of hardness.

In fact, perhaps you have your own scale of hardness named after you using your surname because you are all geologists now.

I love how you got into this exploring the different rocks, carrying out the scratch tests, observing carefully, what are scratches?

Is there any material that had been scratched away?

And in organizing your rocks into the scale of hardness.

It was great to find out about Friedrich Mohs and perhaps people in the future will be finding out about you.

Maybe your name will be the name that people talk about as a famous geologist from the past.

I really hope you enjoyed this lesson.

I very much enjoyed teaching you and I'm really looking forward to seeing you at another lesson soon.

Until then, stay curious.