Question

Short Answers (5pts)

1. What is the model that is used to provide the fundamental discussions of material elements?

2. What types of primary and secondary forces/bonds contribute to the formation of liquid water?

3. What types of primary and secondary forces/bonds contribute to the formation of solid polyethylene?

4. What type of atomic crystal lattice structure is iron at room temperature?

  

5. What type of atomic crystal lattice structure is pure aluminum at room temperature?

6. What type of atomic crystal lattice structure is alumina at room temperature? Topologically, how does its lattice structure differ from that of pure aluminum? What is the consequence (e.g. how is their material characteristic different)?

7. Among the three common crystal lattice structure types of metals, which one exhibits the largest atomic packing?

8. For each of the three common crystal lattice structure types of metals, list one of the most close-packed crystallographic planes.
9. What is diffusion, and what is the most important driving force of diffusion of material?
10. Give an example of a perfectly-elastic material.

Answer 1

1. What is the model that is used to provide the fundamental discussions of material elements?

          Bonding model.

2. What types of primary and secondary forces/bonds contribute to the formation of liquid water?

        Covalent bonds between H and O are primary forces ; and H-bonds with dipole-dipole interaction are secondary forces (IMF).

3. What types of primary and secondary forces/bonds contribute to the formation of solid polyethylene?

Covalent bonds between C - H and C-C are primary forces ; and van der waals (London forces) are secondary forces (IMF).

4. What type of atomic crystal lattice structure is iron at room temperature?

      At room temperature atomic crystal lattice structure of iron is body-centered cubic. (BCC).

5. What type of atomic crystal lattice structure is pure aluminum at room temperature?

At room temperature pure Aluminum has the face-centered-cubic crystal structure. (FCC)

6. What type of atomic crystal lattice structure is alumina at room temperature? Topologically, how does its lattice structure differ from that of pure aluminum? What is the consequence (e.g. how is their material characteristic different)?

Alumina (Al2O3)    Oxygen ions form a nearly hexagonal close-packed structure with the aluminium ions filling two-thirds of the octahedral interstices. Each Al³⁺ center is octahedral. In terms of its crystallography. Thus it is a hexagonal Close packing.

7. Among the three common crystal lattice structure types of metals, which one exhibits the largest atomic packing?

Most metals crystallize in one of three very common structures: body-centered cubic (bcc), hexagonal close packed (hcp), and cubic close packed (ccp, also called face centered cubic, fcc).

HCP and FCC both have : 74 % atomic packing. BCC- 68 %.