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Material

physical science Maturity 7-9 Next article →

A material is any substance or mixture of substances that forms an object. Materials can be pure or they can be impure mixtures. They might come from living things or from non-living matter. Materials science is the specific field of study for these substances. Scientists in this field examine the properties of materials and how to use them. Understanding materials is vital because they make up everything in our physical world.

Humans transform raw materials into useful products through several different processes. One method is purification, which involves cleaning a substance to remove impurities. People can also change a material by shaping it into a new form. Sometimes, engineers introduce other materials into a substance to change its characteristics. A process called synthesis can even create entirely new materials from raw ones. In industrial manufacturing, these substances serve as inputs to create complex products.

Materials also serve as a way to chart the history of humanity. Prehistoric history is divided into the Stone Age, the Bronze Age, and the Iron Age. As technology advanced, new eras emerged based on the materials available. The 19th century is known as the steel age. The middle of the 20th century was the polymer age, which is also called the plastic age. The second half of that century became known as the silicon age.

We can categorize materials based on their specific functions and uses. Building materials are used for construction, while insulation materials retain heat inside buildings. Refractory materials are designed for high-temperature applications. Nuclear materials are used for weapons and nuclear power. Aerospace materials are used to build aircraft and other tools for space. Finally, biomaterials are used for applications that interact with living systems. Engineers use a process called material selection to choose the best substance for a task.

Scientists study the internal structure of materials at different length scales. They use tools like microscopy or spectroscopy to see how a material is composed. In engineering, materials are often grouped by their microscopic structure. Metals consist of pure or combined chemical elements with specific bonding. Alloys are mixtures where at least one element is a metal. Crystals are solids where atoms or ions are arranged in a highly ordered crystal lattice. In contrast, glasses are known as amorphous solids.

Other microscopic categories include polymers and plastics. Polymers are materials built from long chains of carbon or silicon. Plastics are a wide range of synthetic or semi-synthetic materials using polymers. Some materials are hybrids, which are combinations of multiple different materials, such as composites. Humans can even engineer metamaterials to have special properties. These are created by tuning the shape, geometry, or arrangement of materials to achieve results not found in nature.

We also classify materials by their large-scale physical properties. Mechanical properties describe how a material responds to applied forces. These include stiffness, strength, toughness, and hardness. Thermal properties describe how a material reacts to heat or temperature changes. This includes thermal conductivity, which is how heat moves through it, and heat capacity. Other important categories include optical, electrical, and magnetic behaviors. Every material can be compared using these different quantitative measures.

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