Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.
Physical
Metals and Alloys
Metals are shiny materials that conduct heat and electricity well, and alloys are mixtures of elements, usually metals, made to improve them.
Learn, discuss, create, buy or invest
The idea
A metal is a material that looks shiny when polished or broken and conducts electricity and heat fairly well. Most metals are ductile, meaning they can be drawn into wire, and malleable, meaning they can be hammered or pressed into shape. A metal can be a pure chemical element such as iron, or an alloy such as stainless steel.
An alloy is a mixture of chemical elements in which at least one is usually a metal. Alloys often behave differently from the pure elements they are made from. The vast majority of metals in everyday products are alloyed to make them stronger, harder or better at resisting corrosion. Some are alloyed simply to lower their cost, like gold mixed with copper. Steel is iron with a little carbon, while bronze and brass are both based on copper.
The atoms in an alloy are held together by metallic bonding. Because they are strong, metals are used in tall buildings, bridges, most vehicles, tools, pipes and railroad tracks. Some alloys have special jobs, such as titanium alloys in aerospace and beryllium-copper alloys for tools that do not make sparks. The science of metals is called metallurgy.
Check yourself
Question 1 of 2
About how long ago is the history of refined metals thought to begin, with the use of copper?
Composition
what it's made of
- Base Metal — The main metal in an alloy, such as iron in steel or copper in bronze.
- Alloying Elements — Added elements, metal or not, such as the carbon in steel, that change how the metal behaves.
- Metallic Bonds — The bonds that join the atoms of a metal or alloy together.
- Crystal Grains — Tiny crystals inside a metal; in some alloys they all match, while in others different crystals mix.
Connection
how it relates
Under Materials
Change
how and why it evolves
- Past
- The history of refined metals is thought to begin with copper about 11,000 years ago. The first known bronze appeared in the fifth millennium BCE. In 1807 Humphry Davy used electricity to isolate potassium and then sodium for the first time.
- Now
- Since the end of World War II, more sophisticated alloys have been developed, and steel alloys are used in everything from buildings to cars to surgical tools.
- Next
- Demand for light, strong alloys and for recycled metals will likely keep growing as vehicles and aircraft try to save weight and energy.