Lesson video

Hello there, and thank you for joining me for today's lesson.

My name is Mrs. Taylor.

Our lesson today is Physical and Working Properties of Materials, and this is part of the Technical Principles Unit.

The outcome: I can explain the difference between physical and working properties in materials.

We have two key words, physical property, which are the characteristics of a material such as appearance and features and the working property, the way in which material responds to an external force or certain environment, it is also often referred to as mechanical properties.

There are two parts to our lesson today, physical properties and working properties.

Let's begin with physical properties.

Material properties describe how a material looks, feels and behaves.

They are important because they help the designer choose the right materials for a product.

If the wrong materials are used, things can break, wear out too quickly or not work properly.

Material properties can be split into two categories: Physical properties, also sometimes called characteristics, and working properties, also sometimes called mechanical properties.

Using the correct materials ensures functional products.

Like people have physical characteristics to describe their appearance, for example, eye colour, skin tone, and hair type, materials have physical properties or characteristics like colour and texture.

It's what you can see or feel without changing what it is.

Sam says, "I have short hair and a piercing in my right ear." Jacob says, "I have afro-textured hair." And Aisha says, "I wear a hijab." Physical properties are the characteristics of a material that can be observed without doing anything to it.

They help us identify and classify materials.

For example, colour: Gold is yellow.

Copper is reddish-brown.

Density: steel is heavy and foam is light.

Here we have a check for understanding.

Which of the following is a physical property of a material? Is it A, a metal rod bends when force is applied.

B, a plastic ruler snaps under pressure.

C, copper is a good conductor of electricity.

Or D, rubber stretches when pulled.

Pause the video and have a go.

Fantastic.

Let's check.

That's right, it's C, copper is a good conductor of electricity.

Well done.

Physical properties, sometimes called characteristics, help us choose the right material for a product.

For example, glass for windows, because it is transparent.

They help in quality control and testing.

For example, checking the density of metal to ensure it is pure.

Gold is used in circuits for electronic devices such as laptops because it is a more efficient electrical conductor than copper.

Here we have another check for understanding.

Why is aluminium often used for making drinks cans? Is it A, it is lightweight and corrosion resistant, or B, it is flexible and elastic.

C, it is very hard and difficult to shape, or D, it is brittle and breaks easily.

Pause the video and have a go.

Wonderful.

Let's check.

That's right, aluminium is often used for making drinks cans because it is lightweight and corrosion resistant.

So the correct answer is A.

Well done.

Types of physical properties include: Appearance, which might include colour, texture, lustre, which is another way of saying shine, and transparency.

It may include density, which is how compact it is, absorbency, which is how well it soaks up, liquid, and conductivity.

And there are two types of conductivity, electrical, which is how well electrons pass through it or thermal, how well heat passes through it.

When choosing appropriate materials for products, it's important to consider its function to ensure materials with appropriate physical properties or characteristics are selected.

A towel is used for drying things, so it needs to be made from an absorbent material, for example, cotton.

A window lets light through a building, so it needs to be made from a transparent material, for example, glass.

Another check for understanding.

Which of the following is a physical property of metal? Is it A, it rusts over time.

B, it reacts with acid.

C, it is shiny and cold to touch.

Or D, it can be made into wires.

Pause, video, and have a go.

Wonderful.

Let's check.

That's right, it's C, it is shiny and cold to touch.

Well done.

Here we have task A.

Part one, define what is meant by physical properties or characteristics of a material.

Part two, give two examples of physical properties or characteristics and why they are important when selecting materials for a product.

And part three, the image shows silk fabric.

Give one use and explain why it is suitable, referring to its physical properties or characteristics.

Pause a video and have a go.

Wonderful.

Let's have a look at some of the answers you may have come up with.

Physical properties are the characteristics of a material that can be observed or measured without changing its structure.

Examples include colour, density and conductivity.

And part two, give two examples of physical properties.

Density is an example.

Metals are dense, making them suitable for structural frameworks.

And thermal conductivity is an example.

Aluminium is a good conductor of heat, so is used in cooking pans.

And part three, silk is used for clothing like dresses because it's smooth texture and natural lustre, which means shine, make it look and feel luxurious.

Well done.

We now move to the second part of our lesson today, working properties.

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

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

A force is a push, pull or twist on a material.

It is applied by something external.

An environment condition is something like heat, moisture, or sunlight.

A force could be bending, cutting or stretching the material like bending wire, cutting fabric or climbing nylon ropes.

An environmental condition could be heat, moisture, or UV light like a polypropylene chair left in the sun or a steel gate exposed to the rain.

Here we have a 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.

Pause the video and have a go.

Great, let's check.

That's right, it's D cutting pine with a saw.

Well done.

Types of working or mechanical properties include: Elasticity, which is returns to its original shape after being stretched.

Toughness, absorbs impact without breaking.

Flexibility, bends without breaking.

Hardness is resistant to scratches.

Ductility, can be drawn into a thin wire without snapping.

And strength, compressive, withstands pushing forces and tensile, withstands pulling forces.

Here we have another check for understanding.

Which of the following is a working or mechanical property of a material? A, copper has a reddish-brown colour.

B, rubber can stretch and return to its original shape.

C, glass is transparent.

Or D, steel has a high density.

Pause, a video and have a go.

Wonderful.

Let's check.

That's right, it's B, rubber can stretch and return to its original shape.

Well done.

Moldable means a material can be shaped easily.

Heated and softened polymers and clay are moldable and can be pressed or formed into different shapes.

Clay is moldable, not malleable.

Malleable is a specific type of moldability seen in metals.

Malleable refers to metal's ability to be hammered and shaped without breaking.

Iron is malleable, not moldable.

Here we have a check for understanding.

Sort the following materials into moldable or malleable: Clay, silicon, gold, aluminium, PET, plasticine, copper, and titanium.

Pause the video and have a go.

Great, let's check and see how you got on.

Moldable would be clay, silicon, PET, and plasticine.

And malleable would be gold, aluminium, copper, and titanium.

And Jacob says, "Remember, malleable usually refers to metals." And we can see that he has written all the metals in the malleable box.

Well done.

Working or mechanical properties help us select materials based on their function.

For example, car tyres are made from rubber.

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

The car tyres are tough which absorbs shock from different terrain.

Flexible, which helps the tyre grip on different surfaces.

Weather resistance, which resist damage from the rain, heat and cold.

And moldable, the tread, or the grip, patterns are easily included.

Here we have a check for understanding.

Why is Kevlar used for bulletproof vests? Is it A, it is flexible and transparent.

B, it is absorbent and soft.

C, it is tough and impact resistant.

Or D, it is brittle and breaks under stress.

Pause the video and have a go.

Great.

Let's check.

That's right, it is C, it is tough and impact resistant.

Well done.

We now move to task B.

Part one, define what is meant by working properties or mechanical properties of a material.

Two, give two examples of a material and its working or mechanical property to explain its suitability.

And three, explain why aluminium is used for drinks cans referring to its working or mechanical properties.

Pause the video and have a go.

Fantastic, let's have a look at some of the answers you may have come up with.

For part one, you may have said, "Working properties describe how a material reacts to external forces such as push or pull or environmental conditions such as temperature." And for part two, you may have said, "Nylon has good tensile strength, which makes it suitable for ropes as they're always being pulled.

Copper is a ductile material and can be drawn into wires easily without snapping." And for part three you may have said, "Aluminium is used for drinks cans because it is easy to shape, malleable and has enough compressive strength to hold liquids under pressure." Well done.

We now have a summary of our learning today.

Physical properties or characteristics describe what a material looks and feels like.

Working or mechanical properties explain how a material reacts to forces and conditions.

Understanding both helps designers choose the right material for the right job.

Malleable usually refers to metals being easy to shape without cracking.

Well done and thank you for joining me for our lesson today.