Lesson video

(no audio) <v ->Hello, hello! How are you today?</v> My name is Dr.

Shorrock, and I am really excited to be learning maths with you today.

We are gonna have a lot of fun as we move through the learning together.

Welcome to today's lesson.

This lesson is from our unit "Measures: Mass and Capacity" and is called "Use whole kilogrammes and grammes to measure the mass of objects." Throughout the lesson, we will be deepening our understanding of these units called kilogrammes and grammes and when we should be using them.

Sometimes, new learning can be a little bit tricky, but don't worry, I am here to support you, and if we try really hard, I know we can be successful.

So, shall we find out? How do we use whole kilogrammes and grammes when we are measuring the mass of objects? These are the key words that we will be using throughout our lesson today.

We've got mass, gramme, and kilogramme, and I'm sure you have heard those words before, but let's practise them anyway, shall we? My turn, mass.

Your turn.

Fantastic.

My turn, gramme.

Your turn.

Lovely.

And my turn, kilogramme.

Your turn.

Beautiful.

Well done.

Mass is a measure of how much matter something contains, and we often measure it by how much something weighs, and the units we use are kilogrammes and grammes.

A gramme is one of the units of measuring mass, and if you've got a paperclip near you or you can ask an adult to find a paperclip, hold it in your hand.

That has a mass of about 1 gramme.

We abbreviate gramme to a lowercase 'g.

' So, when you see that g throughout the course of this lesson, you will know we mean gramme.

A kilogramme is also a metric measure of mass, and it's used to measure objects that are heavier.

If you've ever held a pineapple, that has a mass of about 1 kilogramme, and we abbreviate kilogramme to a lowercase 'k' with a 'g.

' So, if you see kg throughout the course of this learning, you will know we mean kilogramme.

It would be really interesting at some point if you can, to hold a paperclip in one hand and a pineapple in the other and see if you can feel that difference in their mass.

The learning today is all about whole kilogrammes and grammes when we're measuring the mass of objects.

And we're gonna start by thinking about how we use whole kilogrammes and grammes to measure the mass, and then we're gonna move on to think about comparing and ordering objects based on their mass.

In this lesson, we have got these characters who are going to help us.

We have got Aisha, Sophia, and Jacob.

Let's get started.

So, we've got "Jacob and Aisha were on a treasure hunt and had been asked to find something beginning with the letter 'b.

' Jacob found a brick and Aisha found a book." And Aisha is wondering how heavy their objects are.

Ah, and Jacob is reminding her we should be using accurate vocabulary.

So, she means she wonders what the mass of the objects are.

First, they decide to measure the mass of the brick.

Jacob has held that brick, he knows it's heavy.

So, he knows we'll need to measure in kilogrammes, and kilogrammes are used to measure the mass of objects that are heavy.

And Jacob finds a scale that can measure in kilogrammes, and you can see that because it's got a kg in the centre or towards the centre of that scale.

And he places the brick on top of the scale.

What do you notice? That's right.

Jacob is saying, "The brick has a mass of 2 kilogrammes," and we can see that because the arrow is pointed to the 2, and we can see the scale is in kilogrammes.

Then they decide to measure the mass of the book.

Aisha is asking us what do we notice? Hmm? What do you notice? Ah, yes, Jacob is noticing that the arrow is in between 1 kilogramme and 2 kilogrammes.

So, to help Jacob and Aisha determine the mass of the book, we need to look at the relationship between kilogrammes and grammes, and we can use a number line like the one I've got here to help us.

What do you notice about that number line? Hmm? Do you notice there are grammes on the bottom and kilogrammes on the top? The grammes go from 0 to 1000, counting up in 100s, and the kilogrammes goes from 0 to 1.

What does that tell us? That's right.

Aisha has noticed that 1 kilogramme is equivalent to 1000 grammes.

They are the same, they are the same mass.

So, if something weighs one kilogramme and something weighs 1000 grammes, that will be the same mass.

Have you noticed anything else about this number line? Think about where the arrow is pointing now.

That's right, Jacob has noticed that halfway between 0 grammes and 1000 grammes is 500 grammes and 1000 grammes are composed of two equal parts of 500 grammes.

So, that means that half of 1 kilogramme must be 500 grammes.

So, we can use this learning to help us work out the mass of the book.

When objects are heavier than 1 kilogramme, we need to give the measure in whole kilogrammes and grammes.

So, what can we say about the mass of this book do you think? That's right, the arrow is pointing to halfway between 1 kilogramme and 2 kilogrammes.

So, it's more than 1 kilogramme, but it's not quite 2 kilogrammes in mass.

We know that halfway between whole kilogrammes are intervals of 500 grammes.

So, have you got it yet? Do you know the mass of this book? That's right, the mass of the book is that 1 whole kilogramme and another 500 grammes.

We say that the mass of the book is 1 kilogramme 500 grammes.

And we can represent the mass of the book as a bar model just to really understand the fact that we can give our masses in whole kilogrammes and grammes.

So, 1 kilogramme 500 grammes is composed of 1 kilogramme and 500 grammes.

Let's check your understanding.

"Sophia finds a different object starting with 'b.

'" I wonder if you know what it is.

Basketball, isn't it? "The mass of this ball is (humming) kilogrammes (humming) grammes." So, pause the video, maybe go and find someone, and tell 'em what do you think the mass of this basketball is in kilogrammes and grammes.

Pause the video.

When you've done that, press play.

How did you get on? Did you determine that the mass of the ball is 3 kilogrammes 500 grammes? It's more than 3 kilogrammes because the arrow has gone past the 3, and it's reaching that midway point, isn't it, between the 3 kilogramme and the 4 kilogramme? So, we know it's 3 kilogrammes 500 grammes.

"Sophia has got another set of scales here, and she wants to use them to work out the mass of some potatoes, ready to cook them." Because sometimes when we cook, the cooking time depends on the mass of the object we are cooking.

What do you notice about these scales and the mass of the potatoes? Ah, yes, do you notice the arrow is pointing between the 1 kilogramme and 2 kilogramme mark? And yes, these scales are different, aren't they? There are now five equal parts in between the marked kilogrammes.

I'm gonna use our number line to help us again because, remember, a scale is just a curved number line.

What do you notice about this number line? Do you notice grammes on the bottom going up to 1000 and the kilogramme, it's only got one kilogramme? Sophia has noticed 1000 grammes is composed of five equal parts of 200 grammes.

So, let's have a think about that number line and relate it to these scales.

What do we notice? The arrow is pointing to the end of the third equal part of 200 grammes.

So, the mass of the potatoes must be about 1 kilogramme plus three 200 grammes.

So, plus 200, another 200, and another 200.

So, we can say that the mass of the potatoes is 1 kilogramme 600 grammes.

We can represent this mass as a bar model.

You can see that 1 kilogramme 600 grammes is composed of 1 kilogramme and 600 grammes.

Let's check your understanding.

Which of these is the accurate mass for this box of food? So, take care to notice the intervals on the scale and then option A: 2 kilogrammes 100 gramme; option B: 2 kilogrammes 200 grammes; or option C: 2 kilogrammes 20 grammes.

Pause the video, and when you think you know, press play.

How did you get on? Did you notice it has to be 2 kilogrammes 200 grammes because there are five equal parts in between the marked kilogrammes.

Each part is worth 200 grammes, and the arrow is pointing to the end of that first part.

So, it must be 2 kilogrammes 200 grammes.

So, "Aisha has another set of scales and wants to work out the mass of a cake." What do you notice about these scales? So, what is the same about them as before, and what is different? This time the arrow is pointing between the 1 kilogramme and 2 kilogramme mark again, but this time there are four equal parts in between the marked kilogrammes and we're gonna use a number line to help us again.

What do you notice about this number line? Can you see that the number line goes up to 1000 grammes, which is the same as one kilogramme? But this time we have got four equal parts, and 1000 grammes is composed of four equal parts of 250 grammes.

So, let's have a think about that learning and relate that number line to these scales.

What do we notice? That's it, the arrow is pointing to the end of the third equal part of 250 grammes.

So, the mass of the cake is that 1 kilogramme, that whole kilogramme plus three 250 grammes.

So, we can say that the mass of the cake is 1 kilogramme and 750 grammes.

And we can represent this as a bar model again.

You can see 1 kilogramme 750 grammes is composed of 1 whole kilogramme and then 750 grammes, which is part of a kilogramme.

Let's check your understanding.

Could you tell me what the mass of the cabbage is? You might like to find someone and complete the sentence and say it to them.

Pause the video and when you are ready, press play.

How did you get on? Did you work out that the mass of the cabbage is 1 kilogramme and 250 grammes? 1 kilogramme because the arrow has gone past the 1 kilogramme but not got to the 2 kilogramme.

So, that's our whole kilogramme.

And then the arrow is pointing to the end of the first part, and there are four equal parts.

So, that part must be worth 250 grammes.

Your turn to practise now.

For question one, can you work out the mass of these objects, giving your answer in whole kilogrammes and grammes? For question two, can you solve this problem? "Sophia has a watermelon.

Its mass is 1 kilogramme 750 grammes.

Her family eats some of it.

Its mass is now 1 kilogramme.

What mass of watermelon did they eat?" I'd like you to have a go representing that as a bar model and then write and solve the equation.

And for your third question, can you solve this problem? "Aisha has some apples and pears.

The apples have a mass of 2 kilogrammes, and the pears have a mass of 400 grammes.

Aisha puts the apples and pears on the same scales.

What's their total mass?" So, to help you find that out, could you draw a bar model to represent the problem? And then once you've worked that out, can you draw the arrow showing where it should point on these scales? Have a go at all three questions, pause the video, and when you are ready to hear your answers, press play.

How did you get on? Should we take a look? For question one, you were asked to work out the mass of these objects.

So, the basket was 2 kilogrammes 500 grammes; the cushion, 2 kilogrammes 800 grammes; and the cabbage, 1 kilogramme 500 grammes.

How did you get on? Brilliant.

For question two, you were asked to solve a problem.

You were asked to represent it as a bar model, and you can see the whole amount is 1 kilogramme 750 grammes.

It's mass that's left is one kilogramme.

So, the question mark, that's the part that they ate.

So, you were then asked to write and solve the equation.

So, the whole 1 kilogramme 750 grammes, we're gonna subtract the part that was left, 1 kilogramme.

So, that means they must have eaten 750 grammes of the watermelon.

How did you get on with that? Great stuff.

And for question three, you were asked to solve a problem about some apples and pears and finding their total mass.

You were asked to draw the bar model, the apples are one part and the pears are the other part, and then you needed to draw the arrow showing where it would point.

So, we needed to combine those parts to get 2 whole kilogrammes and 400 grammes.

If we look at the scale, we can see that there are five equal parts in between the marked kilogrammes.

Each part would be worth 200 grammes, but we need the arrow to show 400 grammes.

So, it needs to point after the 2 kilogrammes and then two 200 gramme parts after that.

So, that's where the arrow should be pointing.

How did you get on? Brilliant.

Fantastic learning so far, everybody.

You've really deepened your understanding about how we can use whole kilogrammes and grammes when we are measuring the mass of objects.

We're going to move on now to looking at comparing and ordering objects based on their mass.

Let's revisit Jacob and Aisha's objects.

If you can remember, they found a book and a brick, and we wanna have a think about which object has got the lowest mass.

Can you tell? The book had a mass of 1 kilogramme 500 grammes, and the brick had a mass of 2 kilogrammes.

So, which is the lowest? We need to look at whole kilogrammes first when we are comparing because they are the larger unit.

So, we need to look at those before we look at the grammes.

The book has one whole kilogramme of mass.

The brick has two whole kilogrammes of mass.

The book has got less mass.

We say that it is the lightest because 1 kilogramme 500 grammes is less than something that has got two whole kilogrammes.

Let's check your understanding of this.

A true or false question.

"An object with a mass of 3 kilogrammes 100 grammes is lighter than an object with 2 kilogrammes 900 grammes." Do you think that's true or false? And then why? Is it because 900 grammes is greater than 100 grammes? Or is it because 3 kilogrammes is greater than 2 kilogrammes? Press pause on your video, and when you think you know, press play.

How did you get on? Did you realise that it was false? Because an object with three kilogrammes has got to be greater than an object with 2 kilogrammes.

3 kilogramme 100 grammes is greater than 2 kilogrammes 900 grammes.

Because we look at those whole kilogrammes first when we are comparing.

So, now we've got Jacob, Aisha, and Sophie, and they've each found a rock, and they want to put them in order of mass, starting with the lightest.

And they're each using a different scale.

Have you noticed that? Take a moment.

What do you notice about each of their scales? They are all different, aren't they? They're all going up in different intervals.

We're gonna start with Jacob, and he's saying his rock is the heaviest because it's mass is 2 whole kilogrammes.

And we can see that quite clearly on his scale because the arrow is pointing directly to the 2.

Aisha has a go at measuring the mass of her rock, and she has noticed that on her scale, there are four equal parts and each part is worth 250 grammes.

So, the mass of her rock is 1 kilogramme 250 grammes because that arrow is pointing to the end of the first part after 1 kilogramme.

And for Sophia's rock, her scale is different again.

She has got five equal parts.

So, each part is worth 200 grammes.

And we can see that arrow is pointing to the end of the fourth part after 1 kilogramme.

So, her rock has a mass of 1 kilogramme 800 grammes.

So, the children then put their rocks in order of mass, starting with the lightest.

Do you agree? Hmm.

Ah, "Wait!" says Jacob.

"We started with the heaviest." They were asked to put them lightest first, weren't they? They need to reorder them.

Ah, now they've put their rocks in order of mass, starting with the lightest.

We can see Aisha and Sophie's rocks, both of those have a mass of 1 kilogramme, and Jacob's is 2 kilogrammes, so his is heavier.

But then if we look at Aisha and Sophia's rocks, well, Aisha's has got the least mass because it's got 250 grammes, where Sophia's has got 800 grammes.

So, even though they've both got 1 whole kilogramme, we then need to look at the grammes to be able to compare them.

So, we can say 1 kilogramme 250 grammes is less than 1 kilogramme 800 grammes, which is less than 2 kilogrammes.

So, let's check your understanding.

Out of these three options, can you tell me in which of them have the masses been put into the correct order, lightest to heaviest? Take good care when you are looking at them, pause the video, and when you are ready to find the answer, press play.

How did you get on? Yes, it was option B.

That's the only one where the masses have been put into the correct order from the lightest to the heaviest.

900 grammes, that's not even got a whole kilogramme, so it's less than 1 kilogramme.

And then 1 kilogramme must be less than 1 kilogramme 200 grammes.

Well done.

Okay, it's your turn to practise now.

For question one, can you have a look at these given masses and could you put them in order, starting with the lightest? And for part B, can you find the difference then between the heaviest and lightest mass? For question two, can you look at these boxes and the scales that they are on? Could you tick the box with the greatest mass? And then can you work out what the total mass of the boxes would be? Pause the video, have a go at questions one and two, and when you are ready for the answers, press play.

Shall we see how you got on? So, to begin with, you are asked to look at some masses and put them in order, starting with the lightest.

500 grammes 'cause there's no whole kilogrammes there, then 1 kilogramme, then 1 kilogramme 500 grammes, 2 kilogrammes 250 grammes, and then 2 kilogrammes 500 grammes.

And then you are asked to find the difference between the heaviest and the lightest mass.

I could represent this as a bar model, and I can see that 2 kilogramme 500 grammes is composed of 500 grammes, but the missing part must be 2 kilogrammes.

For question two, you are asked to look at these boxes and tick the box with the greatest mass.

So, I worked out the masses.

The arrow for the first box was pointing to the three.

So, that has a mass of three kilogrammes.

And for the second box, the arrow was pointing just after the 1 kilogramme mark, and there are five equal parts.

So, each part must be worth 200 grammes.

So, it's 1 kilogramme 200 grammes.

So, the box with the greatest mass is the first box.

It's got three whole kilogrammes.

You were then asked to work out the total mass of those boxes.

So, again, I can represent this as a bar model.

I've got two parts, and I need to combine them to find the total.

3 kilogrammes, add 1 kilogramme 200 grammes.

Well, I'm going to add the kilogrammes first to get 4 kilogrammes, and then I've still got that 200 grammes.

So, the total mass of the boxes is 4 kilogrammes 200 grammes.

How did you get on with those questions? Fantastic.

Fantastic learning today, everybody.

You have really made good progress with your ability to measure mass in whole kilogrammes and grammes.

We have learned that one kilogramme is equivalent to 1000 grammes.

And if we make connections with the beginning of this lesson, 1 kilogramme is about the mass of a pineapple, and 1 gramme is about the mass of a paperclip.

So, you would need to hold 1000 paperclips in your hand to have the same mass as a pineapple.

Wow.

We can measure the mass of heavy objects in whole kilogrammes and grammes, and we can use our knowledge of 1 kilogramme and 1000 grammes to determine the mass of objects which have a mass in between a whole number of kilogrammes.

It's been really fun learning with you today, and I look forward to learning with you again another time.

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