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(1) What are the different classes of materials? How do you classify materials?

There are four main classes of materials - Metals, Polymers, Ceramics, Composites

Metals are normally solids at room temperature, shiny, good conductors of electricity,ductile, and are moldable. Metals are either elements or mixtures (called alloys). Theirmelting temperatures range from low in the case of lead to high for tungsten. Some

applications of metals electrical wire( aluminum, copper, silver), plumbing (copper),construction beams (steel), cars (steel), consumer goods (cans, utensils, appliances, tools

etc)

Polymers are large molecules with repeating units that are made up mostly of carbon andhydrogen atoms. Many of our food containers are made of polymers. The bottoms of

these containers made of polymers contain a recycle symbol that looks like a trianglemade of three arrows with a number inside. The numbers range from one to seven andindicate the type of polymer. Polymers have low melting temperatures. Properties

They are ductile can be stretched to 1000% of original length), light weight, medium

strength, have chemical stability and low melting point. Applications car tires, Ziplocbags, food storage containers, plumbing (Polyvinyl chloride PVC), consumer goods(calculator casings, TV consoles, shoe soles, Elmers glue, contact lenses etc)

Ceramics are made of metal plus nonmetals. Common ceramics include glass which isamorphous (not arranged in a regular pattern) and tile which is crystalline (a regularpattern). Properties Wear resistant, chemical stability (corrosion resistant), high

temperature strength, high melting point, good insulators, good optical properties.

Applications window glass, aerospace, energy and automotive industry, consumerproducts (pottery, dishes, glassware etc)

Composites are made up of two or more distinct materials such as polymers or ceramics.Examples are: wood, skis, and concrete. Properties high melting point with high

temperature strength (ceramic-ceramic), high strength and ductile with improved wearresistance (metal-ceramic), high strength and ductile (polymer polymer). Applications

plywood, concrete, fiber glass (boats), carbon fiber resins (bicycle frames)

(2) For each material, indicate its material class.quartz 3 Material Classes:

steel 2 1. polymer

Teflon 1 2. metal

aluminum 2 3. ceramic

plywood 4 4. composite

fiber glass 4

diamond 3

Zip Lockbag material 1

paper clip 2

polyvinyl chloride (PVC) 1

concrete 4

paper 4

(3)Why would a metal be preferred as a bridge building material as opposed to a ceramic material?


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Metals are less susceptible to brittle fracture and can deform (give a warning) prior to failure.

Brittle fracture is a catastrophic fracture with no warning signs and ceramics are brittle by nature.

(4) What type of structural material is used in manufacture of missiles, aircrafts and space vehicles?

Why?

Ultrahigh temperature ceramic-composites are used as structural material in missiles, aircrafts and

space vehicles. They are metal-nonmetal, covalent bonded compounds that have high melting

point, are strong materials and have excellent oxidation resistance. They are also light weight

with service temperature in excess of 2000 degree centigrade. They also have excellent strength

retention and relative chemical stability at service temperatures.

(5) Describe chemical composition of sodium chloride, bonding and elements involved.

Ionic bonding takes place when sodium and chloride make an ionic compound and it involves

transfer of electron from metal to non-metal.

Here sodium loses electron to make positive ions and chloride gains electrons to make negative

ions.

(6) Describe chemical composition of Methane, bonding and elements involved.

One carbon atom and four hydrogen atoms create methane by covalent bonding. Covalent

bonding takes place in non metals and involves sharing of electrons.

Methane - CH4

H

|

H

C

H|

H


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(7) Describe chemical composition of carbon dioxide, bonding and elements involved.

Carbon dioxide consists of two atoms of oxygen and one atom of carbon. Double covalent bond

is formed when the two oxygen atoms achieve stable structure by sharing two pairs of electrons

as in the diagram below.

Carbon dioxide - CO2

O ==C ==O

(8) Describe chemical composition of hydrogen cyanide, bonding and elements involved.

Hydrogen cyanide consists of an atom each of hydrogen, carbon and nitrogen. The hydrogenhas 1 valence electron, the carbon 4 and the nitrogen 5 for a total of 10

The covalent bond between hydrogen and carbon uses two electrons. The carbon has four, butneeds 8, the nitrogen has two but needs 6, to make a total of 10 electrons. Since the hydrogenalready has the correct complement of electrons, triple covalent bond forms between C and N

This uses four electrons, leaving two electrons in a lone pair on nitrogen

Hydrogen Cyanide - HCN

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