Materials & Their Properties

Wood is one of our oldest and most useful materials, but not all trees are the same. We divide natural wood into two main groups: hardwoods and softwoods. Hardwoods come from slow-growing trees with broad leaves, like oak or NZ's native rātā. Because they take a long time to grow, they are dense, expensive, and great for high-quality furniture that needs to resist scratches.

Softwoods come from fast-growing evergreen trees with needles and cones, like pine. Because pine trees grow incredibly fast, softwoods are cheaper and easier to cut, making them the perfect choice for building the timber frames inside house walls.

We also have manufactured boards like MDF and plywood. These are human-made by gluing wood fibers or thin layers of wood together. They are fantastic because they come in huge, perfectly flat sheets that do not warp, twist, or split like natural timber often does.

Metals are shiny, strong, and great at conducting heat and electricity. We group them into two types: ferrous and non-ferrous. Ferrous metals contain iron. This means they are magnetic and can rust if they get wet. Steel is a classic ferrous metal used to build skyscrapers and car frames.

Non-ferrous metals do not contain iron. They will not rust, and they are not magnetic. Examples include aluminum (used in drink cans because it is lightweight) and copper (used in electrical wires because it is highly conductive).

Sometimes, pure metals aren't quite right for a job. To fix this, scientists mix different metals together to create alloys. For example, stainless steel is an alloy of iron, carbon, and chromium. This clever mixture gives us a metal that is incredibly strong but will never rust, making it perfect for kitchen sinks and cutlery.

Plastics are highly versatile synthetic materials made from crude oil. They fall into two totally different families: thermoplastics and thermosetting plastics. The easiest way to remember the difference is to compare them to chocolate and cake batter.

Thermoplastics are like chocolate. When you heat them up, they melt into a runny liquid that you can mold into shape. When they cool down, they set solid. If you don't like what you made, you can simply heat them up and melt them again. This makes them highly recyclable and perfect for things like LEGO bricks and drink bottles.

Thermosetting plastics are like cake batter. Once you bake them (heat them up), they undergo a permanent chemical reaction and set solid. If you try to heat them up again, they won't melt—they will just burn and char. Because they resist heat so well, we use them for things like saucepan handles and wall light switches.

To choose the perfect material, designers look at its working properties. These are the physical rules of how a material behaves under different forces. For example, a trampoline mat needs high elasticity so it can stretch and snap back into shape without permanently deforming.

People often confuse hardness with toughness, but they are very different. Hardness is how well a material resists scratches and dents. Glass is extremely hard, but it is not tough at all! Toughness is the ability to absorb a sudden blow without breaking. If you drop a glass on concrete, it shatters instantly because it has low toughness. A plastic cup might scratch easily (low hardness), but it won't break because it has high toughness.

Other properties include malleability (the ability to be rolled or hammered into flat sheets) and ductility (the ability to be pulled into long, thin wires). Copper is highly ductile, which is why it can be pulled into the thin wires used to charge your devices.

Sometimes, one material on its own just isn't strong enough. In these cases, we create composites. A composite is made by bonding two or more different materials together to create a brand new material with the best properties of both.

Think of concrete reinforced with steel bars. Concrete is amazing when you squish it (compression), but snaps easily if you bend or pull it (tension). By embedding steel rods inside the concrete, we get a composite building material that can handle both heavy weight and bending forces without cracking.

Textiles are materials made from fibers that are woven or knitted together. They can be natural, like wool from sheep and cotton from plants, or synthetic, like polyester made from plastics. They are flexible, lightweight, and perfect for making school uniforms, sports gear, and even heavy-duty sails for yachts.