Lesson video

Hi there everybody.

My name is Mr. Booth.

Welcome to your design and technology lesson for today.

It's great that you could join me.

We've got a brilliant lesson where we are gonna be looking at the working properties of materials.

We're also gonna look at how important it is to be able to understand what working properties are so we can select the appropriate materials for the products that we are designing.

This lesson is part of the materials testing unit.

Today's outcome, I want you to be able to identify working properties of materials.

We have three keywords for you today.

The first is working property, the way in which a material responds to an external force or sometimes certain environments.

This is also sometimes referred to as mechanical properties.

We then have force a push, pull, or twist that acts on an object.

And finally material, what a product is made from.

So keep a look out for those keywords throughout this lesson.

We have two learning cycles today.

The first is all about working properties, and then we're gonna look at how we can select materials based on those working properties.

So let's get going.

Material properties describe how a material looks, feels, and behaves, they're important because they help the designer choose the right materials for the right product.

If the wrong materials are used, things can go wrong pretty quickly.

They can break, wear out too quickly, or not work properly at all.

And you can see here we have a discarded umbrella because it failed.

Now, if the designer had considered more materials than possibly this product wouldn't have broken and it wouldn't have been thrown away and it'd still be in use now.

Working properties describe how a material responds to forces or environmental conditions.

Working properties are also called mechanical properties because they relate to how materials behave when in use.

Now a force is a push, pull, or twist on a material and it's applied by something external.

And this could be, for example, like a compressive force, and we also have an environmental condition.

This could be something like heat or moisture, for example, if it's left outside or even sunlight.

Now let's have a look at some examples of these two conditions.

So a force could be bending, cutting, or stretching a material.

Some examples could be bending wire to form a piece of artwork.

Cutting fabric if you're gonna make a garment or maybe climbing nylon ropes.

They are all forces acting upon those materials For environmental conditions, this could be heat, moisture, or even UV light.

Like for example, a polypropylene chair that's been left in the sun or a steel gate that's exposed to the rain.

Quick check for understanding, which of the following is an example of a force acting on a material.

Is it A, sunlight fading fabric, B, rain causing steel to rust, C, humidity making paper curl, or D, cutting pine with a saw, so which of those is a force? Pause the video now, have a go at this, and come back to me when you've got your answer.

It is of course D.

Cutting pine with a saw, well done.

Now let's have a closer look at the different types of working properties.

Remember we sometimes call these mechanical properties, but these can include elasticity.

This is when a material will return to its original shape after being stretched.

Think of an elastic band.

If you stretch an elastic band and then let go of it, it will return to its original shape unless of course you stretch it way too far, and then it'll of course break.

We then have toughness.

This is a material's ability to absorb impact without breaking.

Think of hitting a piece of aluminum with a hammer.

We then have flexibility, the ability of a material to bend without breaking.

We have hardness.

This is a material's ability to withstand scratches or indentations.

Ductility, this is the ability of a material to be drawn out into thin wire without snapping.

So for example, like copper wire.

And then we have strength.

Now strength can be broken down into a number of different properties.

And in this case we're looking at tensile strength.

When a material resists a pulling force and we have compressive strength.

And that's whether materials withstanding a pushing or a squashing force, if you like, you also have torsional strength, and that's a twisting force.

Check for understanding, which of the following is a working property of a material? Is it A, copper has a reddish brown color? B, rubber can stretch and return to its original shape? C, glass is transparent, or D, steel has a high density? Pause the video now, have a go at this, and come back to me when you've got your answer.

It is of course B, rubber can stretch, and return to its original shape.

That is of course elasticity.

So we're now onto your first task.

What I would like you to do is fill the table to show which tests could be used to examine each of the listed working properties.

So let's have a look at our properties and our definitions and our tests.

So first of all, we have elasticity.

And the definition of course is the material returns to its original shape after being stretched.

And the test for this could be stretch or compressed and released and see if it returns to its original shape.

We then have strength with the definition withstand forces 'cause remember we've got compression and also we've got tensile strength.

We've then got toughness, absorbs impact without breaking.

We've got flexibility, bends without breaking.

Hardness, resistant to indentations and scratches.

And of course, ductility can be drawn out into a thin wire without snapping.

So what I want you to do is think of some tests that could be carried out to examine those types of properties.

Pause the video now, have a go at this, and come back to me when you've got your answers.

So how did you get on? Well, let's have a look at some samples.

Here are my answers.

So obviously elasticity, we already did that.

So let's have a look at strength withstand forces.

Well, you could apply weight, you could pull, you could bend it.

You could even twist it until it breaks to see how strong it is.

Toughness, this is all about absorbing impact without breaking.

Well, you could likely hit a material with a mallet or bend it repeatedly.

That's one way you could test its toughness.

We then have flexibility, bends without breaking.

Well, that's quite obvious.

You could bend and twist by hand.

We then have hardness, resistant to indentation and scratches.

Well, you could use a scribe to scratch it or indent it with a center punch and a hammer.

And finally we have ductility the ability of it to be drawn out into a thin wire without snapping, well you could try stretching small pieces of it, and see if it'll go into a thin shape.

So that's lots of different ways that you could test these.

Well done.

So we're now onto selecting materials based on their working properties.

Now, working properties help us select materials based on their function.

For example, car tires are made of rubber.

They determine how materials behave under stress and in different environments.

So let's have a look closer at this car tire.

Well, they're tough.

They absorb shock from different terrain.

They're flexible.

They help the tire grip on different surfaces.

They're weather resistant, resistant to damage from rain, heat, and also the cold.

And of course they're moldable.

The tread, the grip patterns are easily included when these are manufactured.

Now, moldable means a material can be shaped easily.

A good example of this is clay.

It is moldable and can be pressed and formed into different shapes.

I'm sure you probably at some point had a go with that.

Now, malleable is a specific type of moldability that is seen in metals, and it's important that you know the difference between the two.

And malleable refers to a metal's ability to be hammered and shaped without breaking.

And a good example of this is, of course, iron, which is, of course, malleable but not moldable.

And clay is of course, moldable but not malleable.

So it's important you understand the difference between the two of those.

So quick check for understanding, which of these materials is moldable? Is it A, plasticine, B, pine, or C, aluminum? Pause the video now, have a go at this, and come back to me when you've got your answers.

It is of course plasticine.

That is definitely moldable.

Now every material has its own unique set of working properties, which determine why it's suitable for a particular use.

So in this case, we have an aluminum can.

So let's look at the material properties, the working properties of aluminum to see why it's suitable for aluminum cans.

Well, we know it's aluminum.

It's used for drinks cans.

It's also used for bike frames and also car chassis.

Let's see why that might be the case.

Well, let's have a look at the properties.

It's got a very good strength, very good toughness, very good corrosion resistance, very good thermal and electrical conductor.

And it's lightweight when compared to other metals.

So obviously we've got a mix there of working properties.

And also there's physical properties in there as well.

A quick check for understanding.

Select the working properties of aluminum.

We've got A, very good corrosion resistance.

B, a very good insulator.

C, very good toughness.

And D, poor corrosion resistance.

Pause the video now.

Come back to me when you've answered.

So the working properties of aluminum are very good, corrosion resistance, and very good toughness.

Well done.

So now we have the material polypropylene.

This is used for food containers such as a lunchbox you can see here, it's used for seating, and also storage crates.

Now why of course, is it used for all those uses? Well, the properties are, it's got good toughness.

It's got very good corrosion resistance.

It's a good insulator.

It's lightweight.

It's got very good flexibility.

And you know that because of course you've got those little handles on the side which snap down that you flex again and again and they don't break.

But it's got poor hardness.

And that of course means that the surface of this lunchbox will eventually mark and you will see scratches and indentations in it.

Quick check for understanding.

Select the working properties of polypropylene.

We have A, very good corrosion resistance.

B, poor insulator.

C, poor hardness.

D, poor corrosion resistance.

Pause the video now have a go at this and come back to me when you've got your answer.

It is, of course, very good corrosion resistance, and also poor hardness, well done.

Now we have the material pine used for furniture, flooring, doors, and window frames and general joinery.

You might have also used this in your school lives.

The properties of pine.

It's got good strength, good toughness, poor corrosion resistance.

But of course this can be improved if you treat it.

It's a good insulator.

It's relatively lightweight when compared to other timbers.

It's got good flexibility, which means of course it can bend slightly without breaking, but it's got poured hardness, soft wood, it dents easily, it marks easily.

Another check for understanding.

Select the working properties of pine.

We have A, good corrosion resistance.

B, very good hardness.

C, good strength, and D, poor corrosion resistance.

Pause the video now, have a go at this, and come back to me when you've got your answer.

So the working properties of pine are of course good strength, but poor corrosion resistance without treatment.

So we're now into task B.

First of all, I want you to discuss why aluminum is a suitable material for a drinks can to be manufactured from.

I then want you to select four products from below.

And using research, select a suitable material based on physical and working properties.

Explain your choices.

The products you have to choose from are a garden table, a kitchen sink, a T-shirt, electrical wiring, raincoat, support beam in a house, a drinks cup, a flower pot, a bookshelf, and a picture frame.

Pause the video now have a go at this task and come back to me when you've answered it.

So first of all, I want you to discuss why aluminum is a suitable material for a drinks can to be manufactured from.

And here we have Alex and Jacob with their answers.

Aluminum is lightweight and recyclable.

Ideal for cans, it is malleable, so it can be easily shaped into a can.

Aluminum is corrosion resistant and it's lightweight when compared to other metals.

There are two great answers and the reason why aluminum is suitable.

I then wanted you to select four of the products below and using research, select a suitable material based on physical and working properties.

I wanted you to explain your choices.

So here are some examples below.

First of all, we have the T-shirt.

The appropriate material would be cotton.

Cotton is soft and comfortable against the skin and breathable, keeping the wearer cool.

We then have a flower pot.

Well, you could use PLA, PLA is easy to 3D print the desired shape.

It's lightweight, available in various colors, and is biodegradable.

We then have electrical wiring, and this of course could be copper.

Copper is an excellent conductor and it's ductile, allowing it to be drawn into long continuous wires without breaking.

And then of course we have the garden table and I selected pine.

Pine is strong, easy to shape, and could be treated to withstand outdoor weather.

So that brings us to the end of today's lesson.

Let's have a quick summary.

Working properties describe how materials respond to external forces, such as push, pull, and twist, or environmental conditions such as heat, moisture, or sunlight.

Key working properties include hardness, toughness, strength, flexibility, elasticity, and ductility.

Each showing how a material behaves under stress or change.

Materials can be tested by applying forces or exposing them to environments.

And finally, materials are chosen for products based on their properties.

You've been absolutely fantastic today.

I hope you've enjoyed today's lesson.

I look forward to seeing you all next time, goodbye.