1. Chapter 25
Section 1

2. Alloys An alloy is a mixture of elements that has metallic properties.
You can think of an alloy like music. As you add different instruments you get a different sound. Just like when you add different metals you get different results.
An example would be pewter, which is a mixture of tin, copper, and antimony.
The reason why we make alloys is to improve on the properties of all the metals that go into it.

3. Properties of metals and alloys
Alloys retain the metallic properties of metals.
These properties include:
Luster—reflects light or has a shiny appearance
Ductility—the ability of a metal to be pulled into a wire
Malleability—the ability of a metal to be hammered or rolled into thin sheets
Conductivity—means that heat or electrical charges can easily move through the material

4. Choosing an Alloy
There are many different properties of alloys, to know which one is the correct one to choose you must first know what you will be using it for.
Ex: Gold Ring
One Karat is 1/24 part pure gold
22 Karat ring has 92% gold and 8% copper
14 Karat ring has 58% gold and 42% copper
12 Karat ring has 50% gold and 50% copper
The more copper the strong the ring is but the less it is worth.

5. Uses of Alloys
If you see an object that looks metallic it is most likely an alloy.
Stronger alloys can be used to manufacture industrial machinery, construction beams, and railroad cars and rails just to name a few.
Automobile and aircraft bodies need an alloy that corrosion resistant and lightweight yet durable.
Tooth fillings are made of alloys, usually a mix of silver and mercury .
The pins used to fix a broken limb are special alloys chosen to prevent rejection from the body’s tissues.
Not all are chosen because they are stronger. Wood’s metal is a soft metal that melts around 70°C. It is made from bismuth, lead, tin and cadmium. This low melting point makes it ideal to use in overhead sprinkler systems.

6. Common Alloys
Name
Composition
Use
Bronze
Copper, tin
Jewelry, marine hardware
Brass
Copper, zinc
Hardware, musical instruments
Sterling silver
Silver, copper
Tableware
Pewter
Tin, copper, antimony
Solder
Lead, tin
Plumbing
Wrought iron
Iron, carbon
Porch railings, fences, sculpture

7. Steel
There are various classes of steel; they are classified by how much carbon and other elements are mixed with it.
Typically steel is a strong alloy and is used in things like bridges, overpasses, ship hulls, bed springs. These are all reinforced with steel.
Stainless steel is a type of alloy that is used in cooking utensils, and surgical instruments.

8. New Alloys
Titanium alloy panels are used on the space shuttles as they are very good insulators against heat. These panels are large and easy to attach to the shuttle.
This is a more promising heat shield than the current ceramic tiles are. With the ceramic tiles, people had to be careful and fully inspect the shuttle to check for cracks. If there were any cracks then the tile had to be replaced.

9. Section Check What is a medical use of alloys?
Explain the effects of adding small amounts of another substance to a material.
Why is steel an important alloy?
What are general uses of alloys?
What is the difference between malleability and ductility?