Materials and Their Properties

Everything around you is made from materials — wood, metal, glass, plastic, fabric, stone and many more. Each material has a set of properties: characteristics that describe how it behaves. Scientists and engineers study these properties carefully so they can pick the right material for each job.

Some of the most important properties are hardness (how well it resists scratching), strength (how much force it can take before breaking), flexibility (how easily it bends), transparency (whether light passes through), and how well it conducts heat or electricity. A material can be strong in one property and weak in another.

Engineers choose materials by matching properties to the task. A bridge must be strong and stiff so it does not snap or sag. A frying pan must conduct heat quickly. A raincoat must be waterproof and flexible. A window must be transparent and rigid. Choosing the wrong material could be uncomfortable, wasteful or even dangerous.

Materials can be sorted into natural and synthetic. Natural materials come straight from the Earth or from living things — wood, cotton, wool, stone and clay. Synthetic materials are made by people through chemistry. Nylon, polyester and many plastics are synthetic, designed to have exactly the properties we want.

Some of the cleverest materials are composites, which combine two or more materials to get the best of each. Reinforced concrete puts steel rods inside concrete: the concrete is brilliant at resisting being squashed, while the steel resists being stretched. Carbon fibre is both very light and very stiff, perfect for racing bikes and aircraft.