Imagine playing rugby in flip-flops, or trying to swim laps in heavy steel-toed boots. Sounds ridiculous, right? That is because every single object on Earth needs to be made of materials with the exact right properties for the job.
Words to own
- Property
- A feature or characteristic of a material, like how stretchy, hard, or heavy it is.
- Conductor
- A material that allows heat or electricity to flow through it quickly and easily.
- Insulator
- A material that blocks or slows down the flow of heat or electricity.
- Malleable
- Able to be hammered, pressed, or rolled into thin sheets without cracking or breaking.
- Hardness
- How well a material resists being scratched, dented, or marked.
The Search for the Perfect Fit
Think about your favorite pair of shoes. You wouldn't wear heavy steel-toed boots to go swimming, or flimsy flip-flops to play a tough game of rugby. Different activities require different designs.
Engineers and product designers think the exact same way. Every material around us has its own unique characteristics, which scientists call properties. Choosing the right material for the right job is the secret to good design.
Engineers choose materials by matching properties to the job.
Hover or tap a label above to light up that part of the diagram.
| Point | Conductors | Insulators |
|---|---|---|
| What they do | Let heat and electricity pass through easily | Block or slow down heat and electricity |
| Common materials | Metals like copper, iron, aluminium, and gold | Plastic, rubber, wood, and glass |
| Where to find them | Saucepan bases, inside electrical wires, radiators | Saucepan handles, wire coatings, oven mitts |
| Particle behavior | Have free particles that pass energy along quickly | Hold onto energy and do not pass it on easily |
The Big Six Properties
There are six key properties that scientists look at when testing new materials. First is hardness, which is how well a material resists scratches. A diamond is extremely hard, while talc is very soft.
Next is flexibility, the ability to bend without breaking and return to shape. Strength tells us how much force a material can take before it snaps. Transparency describes whether light can pass through, like see-through glass versus solid wood.
Conductivity is how easily heat or electricity travels through a substance. Finally, malleability is the ability to be hammered flat. Aluminium is highly malleable, which is why we can roll it into paper-thin kitchen foil.
Perfect Partnerships: Combining Materials
No single material is perfect for every single job. This is why designers often combine materials with totally different properties into one clever object.
Take a kitchen saucepan. The base is made of metal because it needs to be a good thermal conductor, passing heat from the stove into your food. But a metal handle would burn your hand. To solve this, the handle is made of plastic or wood—excellent insulators that stay cool to the touch.
We see the same partnership in electrical wires. The inside is a metal wire that conducts electricity, while the outside is a plastic coating that insulates the wire, keeping the electricity safely inside and protecting you from shocks.
The Smart Choice vs. The Best Choice
You might think engineers always choose the absolute strongest or most conductive material available, but real-world design involves compromises.
For example, gold is actually a better electrical conductor than copper. However, almost all household wires are made of copper. Why? Because gold is incredibly expensive! Copper is cheap, abundant, and almost as good, making it the smarter practical choice for everyday life.
Try it yourself · 15 minutes
The Great Spoon Race
You need
- One metal spoon
- One plastic spoon
- One wooden spoon
- A mug of warm water
- Three tiny dabs of butter
- Three small beads or dried peas
Method
Myth-busting corner
MythHeavy things are always stronger than light things.
TruthCarbon fiber is extremely light but much stronger than many heavy metals. Weight and strength are separate properties.
MythThermal insulators keep things cold, but not hot.
TruthInsulators simply slow down the transfer of heat. They work both ways: keeping hot soup hot, or keeping cold ice cream frozen.
Exam answer that scores full marks
Explain why a saucepan is often made of metal with a plastic handle.
A saucepan's base needs to transfer heat efficiently from the stove into the food, so it is made from metal—a good thermal conductor. However, metal also gets dangerously hot to touch. If the handle were metal too, it would burn your hand. To solve this, the handle is made from plastic (or sometimes wood), which is a poor conductor of heat (an insulator), so it stays cool enough to hold safely even while the base is very hot. This shows how designers combine materials with different, complementary properties within a single object.
Why it scores
- Clearly identifies metal as a good thermal conductor for cooking food.
- Explains that plastic acts as an insulator to prevent heat from reaching the hands.
- Demonstrates an understanding of why combining materials with different properties is useful in product design.