Unformatted text preview: melting temperature?
24. Given that the coefﬁcient of expansion for Al is 25 10 6 C 1 and for SiC is
4.3 10 6 C 1, predict which material has the higher melting temperature.
25. Explain why it is difﬁcult to ﬁnd a material with both a high stiffness and a high
coefﬁcient of thermal expansion.
26. Many, many oxide ceramics or ionic solids have moduli of elasticity of 6.9 10 4
MPa, independent of composition. Why?
27. The modulus of elasticity of window or oxide glass is 6.9 10 4 MPa and that of a
“plastic” glass is 6.9 10 3 MPa. How much more will the plastic glass deﬂect than the
oxide glass under a given load?
28. Sketch a bond-energy and bond-force curve for a material with a negative thermal expansion coefﬁcient.
29. The center-to-center separation of two atoms in pure Ti is 2.94 `. The thermal expansion coefﬁcient of Ti metal is 9 10 6 C 1. What percent increase in atomic separation is realized in going from 25 C to 625 C? Repeat the problem for copper, using data
from Table 2.5–1 and Appendix C.
30. How might a scientist or an engineer measure Young’s modulus in the laboratory? How
about the thermal expansion coefﬁcient? | e-Text Main Menu | Textbook Table of Contents pg058 [V] G12 7-27060 / IRWIN / Schaffer 58 Part I 39.
45. js 1-27-98 plm 3-21-98 MP Fundamentals c. If you were told that the observed CN for the anion was 6, what would you conclude
about the nature of the bond?
Two elements are combined and the coordination number of each type of atom is 12.
What is the relative size of each atom type?
How many bonds form with C? How many with Si? Is it reasonable to expect that Si
can be substituted for C in most organic structures, so that silicon chemistry has at least
some similarities to carbon chemistry?
Show the correct geometrical structure of C2 H6 .
Why are there no solids with coordination number 5, 7, or 9?
Where would you put four tacks in a cubic room if you wanted each of them to be as
far from the others as possible?
Discuss the value of the bond angle (H @ N @ H) in ammonia, NH3 .
If you add a proton, H ,...
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