EXPLORING PROPERTIES OF MATERIALS

POLYMERS & COMPOSITES Organic compound – a compound containing atoms of carbon bonded to one another and to other kinds of atoms (ex. – hydrogen, oxygen, nitrogen). *Carbon is present in more than 2 million known compounds!

Carbon can form this many different compounds because of 2 properties: (1) carbon atoms can form 4 covalent bonds (maximum) (2) carbon atoms can form chains, branched chains, and rings

Polymer – a large, complex molecule built from smaller molecules bonded together. Monomer – the smaller molecules from which polymers are built. Polymers form when chemical reactions link monomers in a repeating pattern.

What are some natural polymers? Cellulose – fibers that make up cell walls of plants.

Animal polymers: spider webs, silk, wool, fingernails, etc Animal polymers: spider webs, silk, wool, fingernails, etc. (all protein compounds)

Synthetic Polymers The starting materials for most polymers are coal and oil. Plastics – common synthetic polymers that can be molded or shaped. Synthetic polymers include: carpet, clothing, adhesives, insulation, etc. [Figure 5 – page 71]

Composites Composites combine two or more substances as a new material with different properties. By using two or more substances in a composite, chemists can make a new material that works better than either one alone.

A Natural Composite Wood is a common natural composite. Wood is made from cellulose and lignin.

Synthetic Composites Examples: Fiberglass Graphite composites carbon nanotube composites

METALS & ALLOYS Alloy – a mixture made of two or more elements that has the properties of a metal. What are the properties of metals? The properties of an alloy can differ greatly from those of its individual elements.

Alloys are generally stronger and less likely to react with air or water than pure metals. Bronze Cymbal Brass Trumpet

Other common alloys include: carbon steel stainless steel plumber’s solder sterling silver dental amalgam pewter [Figure 9 – page 82]

Ceramics & Glass Ceramics – hard, crystalline solids made by heating clay and other materials to high temperatures. Properties of Ceramics: Ceramics are brittle Ceramics resist moisture Ceramics do not conduct electricity Ceramics can withstand extremely high temperatures

Uses of Ceramics Food storage Roofing tiles Bricks Sewer pipes Insulators in electric equipment & light fixtures Oven walls Space shuttle insulation

Glass Glass – a clear, solid material with no crystal structure, created by heating sand to a very high temperature. Uses of Glass: Windows Bottles & jars Lenses Cooking surfaces & cookware Laboratory glassware Optical fibers

Optical fiber – a threadlike piece of glass or plastic that can be used for transmitting light. The light that moves through an optical fiber is reflected within the fiber. A pair of optical fibers the thickness of a human hair can carry 625,000 phone calls at one time. One quarter pound of glass fiber can replace over two tons of copper telephone and cable television lines.