Ch. 12
1. 3-4 students per table
2. Workbook & Textbook
3. Pencil / Pen
4. Start when quiet
Ch. 12
1.
2.
3.
4.
Wood
Modified Wood
Metals & Alloys
Plastics
Text / Work Books
Text Book – p. 373
Work Book - p. 199
• Copy the following definitions
WOOD
• Is a material that comes from cutting and
processing trees (p. 373)
MODIFIED WOOD
• Is treated wood or a material made with wood
mixed with other substances
WOOD vs. MODIFIED WOOD:
WOOD
MODIFIED WOOD
Mechanical Properties
Hardness
• Hardwood is harder than softwood
• Healthier trees have a higher level of hardness
Elasticity
• Wood usually has good elasticity
• It can suffer many impacts without becoming
permanently deformed
Resilience
• When wood has adequate moisture content it
is resilient and resistant to breakage
• When wood is dry it breaks easily
4. HARDNESS, ELASTICITY,
RESILIENCE & TOUGHNESS
Ductility
• Wood has very little to no ductility
Malleability
• Heat increases the malleability of wood.
• A plank or piece of wood can be bent if it is
heated to a certain amount
Wood Bending
Tensile Strength
• Wood has excellent tensile strength so it is
often used to support heavy loads.
• Hardwood has more tensile strength than
softwood.
Floor Joists
Factors affecting the mechanical…
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Species of tree
Growth rate of tree
Moisture content of tree
Injuries sustained by tree (fungi, insects, etc)
1. SPECIES OF TREES
HARDWOOD
SOFT WOOD
2. SPEED OF GROWTH
HEARTWOOD
SAPWOOD
3. WATER CONTENT
Injuries
• Fungi
• Insect
• Microorganism
Pine Beetle
Reasons wood is commonly…
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Wood is easily worked
Wood is easily assembled
Wood is a good thermal insulator
Wood does not conduct electricity
EASILY WORKED & ASSEMBLED
LOW THERMAL CONDUCTIVITY
LOW ELECTRICAL CONDUCTOR
Principal Species of Wood…
Hardwood
Maple
Yellow Birch
Oak
Principal Species of Wood…
Softwood
Spruce
Pine
Cedar
Modified Wood
Treated Wood
Laminated Wood
• Is made by gluing small pieces of wood
together
Plywood
• Is made by gluing together large sheets of
wood
Particle Board
• Is made with wood chips and wood waste
• Particles are bonded with various products
Fiberboard (MDF)
• Is made by first separating wood fibers (very
fine sawdust)
• Fibers are bonded with various products
Advantages
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Stable mechanical properties
Weather resistant
Used to manufacture large materials
Made from small trees
Made with wood chips and wood waste
A METAL
• Is a material extracted from an ore.
• Usually shinny and are good conductors of
electricity and heat
AN ALLOY
• Is the result of mixing a metal with one or
more metallic or non-metallic substances
A Ferrous Alloy
• An alloy whose main constituent is iron
A non-Ferrous Alloy
• Is an alloy whose main constituent is a metal
other than iron
Common Metals
Iron
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Silvery
Soft
Can rust if exposed to oxygen
Most commonly used metal
Copper
• Red-brown
• One of the best conductors of electricity
Aluminum
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White
Soft
Very abundant in nature
Most commonly used metal after iron
Zinc
• White, slightly bluish
• Corrosion resistant
Magnesium
• Silvery white
• Can burn on contact with air
• Fireworks
Nickel
• Grey
• Corrosion resistant
• Coins
Chrome
• White, slightly bluish
• Surface coating
• Car parts
Tin
• Silvery white
• Welding
• Utensils
Common Alloys
Steel
• Mix of iron and carbon
• Less than 1.5% carbon
Cast-Iron
• Mix of iron and carbon
• Over 2% carbon
Brass
• Mix of copper and zinc
• Can take on various colours according to metal
content
Bronze
• Mix of copper and tin
• Colour varies from yellow to red to brown
Aluminum Alloy
• Many aluminum alloys to which a small
amount of one or more substances has been
added
Wood, modified wood, ceramics,
metals and alloys lab
1. Work with table groups
2. Write ALL names on hand-out
3. Hand in at the end of lab
Homework
• Workbook - p. 199-205