Ways that Alloys are Used

Brass Instruments

• Musical instruments made of hard brass alloys have bright sound quality.  If they were made of soft copper, the sound would be deadened and dull.

• Chromium and nickel can be added to steel to harden it, also fighting corrosion.  If steel is made with eighteen percent chromium and eight percent nickel, the metal hardly rusts at all.
• The chromium + nickel oxides form a protective coating.  Since this type of alloy doesn't "stain," it is called stainless steel.
• Tungsten carbide is used to make surgical tools because surgeons need the cutting edges of these tools extra sharp.

Metal Compounds and Mixtures

Rust

Tarnished Silverware

What happens of iron rust or when silver and copper form a blackish tarnish?  In these cases, the atoms of a metal have combined with atoms of a nonmetal.  This process is called corrosion.  Corrosion is the gradual "eating away" of a metal because it reacts chemically to form a compound that weakens it.


The most reactive metals are the quickest to corrode.  Sodium metal must be stored under oil to keep the sodium metal from reacting with oxygen within seconds.  

Most of the time, metals aren't used as their elemental form.  While still, melted, other metals and nonmetals are added to form an alloy, which is the mixture of two or more metals and nonmetals.  For example, gold is too soft  to make durable jewelry.  When mixing gold with copper, silver, nickel, or palladium, the gold gets harder.

Fun Facts:

• Pure copper is only used for wires to conduct electricity.



Copper Wire

• The use of bronze helped civilizations grow in size and power, and this time in history is called the Bronze Age.

How Hard are Metals?

Each metal has a different hardness.  

Gold

Copper

Any metal that can be rolled or pounded into flat sheets is said to be malleable.  Any metal that can be drawn out into strands of wire is said to be ductile.  Copper and god are in the group with the most malleable and ductile metals.

Not all metals are hard.  Sodium metal can be cut with a butter knife.

The hardness of metals is measured by denting them.  The size of the dent indicates the hardness.  Chromium is the hardest metal in pure elemental form.  Cesium is the softest metal.

Metals have in Common

Metals have good electrical conductivity.  This means that they let electricity flow through them easily.  Nonmetallic materials resist the flow of electricity through them.  For this, nonmetals are good insulators, which can prevent movement of heat, energy, and even sound.  Electrical wires made of copper or aluminum are made because these elements are some of the best electrical conductors of all metals.

Maglev Train

A superconductor is an element at temperatures way below freezing and they lose all resistance to electrical flow.  Superconductors are used today in maglev trains that float above the rails on supermagnets.

Metals

Metals take up about three-fourths of the periodic table of elements, of 75%.  Some familiar ones are gold, copper, silver, zinc, aluminum, iron, lead, mercury, magnesium, and chromium.
A metal is a substance that is a good conductor of heat and electricity.
The melting points of metals are in a wide range of temperatures.

Beryllium

Metals with high melting points are useful because they can withstand high temperatures.  The aerospace industry uses beryllium to stop space shuttle as it lands.