Mr. Rogers' IB Design Technology Objectives
Timber - natural wood or composite (plywood, masonite, particle board)
  1. Describe the structure of natural timber
  • cellulose fibers: the light colored part of the grain structure. Used for making paper, rayon (artificial silk), photographic film (cellulose acetate), cigarette filters (cellulose acetate).

  • lignin matrix: the dark colored part of the grain structure. Used for making masonite

  1. Outline the broad categories of trees and their related types of lumber.

  • conifer trees--softwoods: grow only in temperate regions.

  • deciduous trees--hardwoods: grow in both temperate and tropical regions.

  1. List examples of composite timbers and discuss their properties and merits.

  • plywood

  • particle board (chipboard)

  • laminated woods

  • masonite

  1. Outline criteria for the selection of timber for different structural and aesthetic design contexts.

  2. Describe the reasons for treating or finishing wood.

  • reducing attack by organisms and chemicals,

  • aesthetics

  • modifying other properties.

  1. Explain three differences in the selection of timbers for flooring if it were made of a hardwood, a softwood or a composite material.

  • durability,

  • ease of maintenance

  • aesthetics.










Draw and describe a metallic bond.

Explain why metals are very good electrical and thermal conductors. (It's the movement of free electrons.)

Describe the physical  structure of pure or alloyed metals.

  • crystaline--highly organized arrangements of atoms

  • composed of numerous grains--small crystalline regions

Explain how grain size can be controlled and modified by the rate of cooling of the molten metal, or by heat treatment after solidification.

Reheating a solid metal or alloy allows material to diffuse between neighbouring grains and the

grain structure to change. Slow cooling allows

larger grains to form; rapid cooling produces

smaller grains. Directional properties in the

structure may be achieved by selectively cooling

one area of the solid.