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What types of liquids typically form amorphous solids?
At very low temperatures oxygen, O 2 , freezes and forms a crystalline solid. Which best describes these crystals?
(a) ionic
(b) covalent network
(c) metallic
(d) amorphous
(e) molecular crystals
(e) molecular crystals
As it cools, olive oil slowly solidifies and forms a solid over a range of temperatures. Which best describes the solid?
(a) ionic
(b) covalent network
(c) metallic
(d) amorphous
(e) molecular crystals
Explain why ice, which is a crystalline solid, has a melting temperature of 0 °C, whereas butter, which is an amorphous solid, softens over a range of temperatures.
Ice has a crystalline structure stabilized by hydrogen bonding. These intermolecular forces are of comparable strength and thus require the same amount of energy to overcome. As a result, ice melts at a single temperature and not over a range of temperatures. The various, very large molecules that compose butter experience varied van der Waals attractions of various strengths that are overcome at various temperatures, and so the melting process occurs over a wide temperature range.
Identify the type of crystalline solid (metallic, network covalent, ionic, or molecular) formed by each of the following substances:
(a) SiO 2
(b) KCl
(c) Cu
(d) CO 2
(e) C (diamond)
(f) BaSO 4
(g) NH 3
(h) NH 4 F
(i) C 2 H 5 OH
Identify the type of crystalline solid (metallic, network covalent, ionic, or molecular) formed by each of the following substances:
(a) CaCl 2
(b) SiC
(c) N 2
(d) Fe
(e) C (graphite)
(f) CH 3 CH 2 CH 2 CH 3
(g) HCl
(h) NH 4 NO 3
(i) K 3 PO 4
(a) ionic; (b) covalent network; (c) molecular; (d) metallic; (e) covalent network; (f) molecular; (g) molecular; (h) ionic; (i) ionic
Classify each substance in the table as either a metallic, ionic, molecular, or covalent network solid:
| Substance | Appearance | Melting Point | Electrical Conductivity | Solubility in Water |
|---|---|---|---|---|
| X | lustrous, malleable | 1500 °C | high | insoluble |
| Y | soft, yellow | 113 °C | none | insoluble |
| Z | hard, white | 800 °C | only if melted/dissolved | soluble |
Classify each substance in the table as either a metallic, ionic, molecular, or covalent network solid:
| Substance | Appearance | Melting Point | Electrical Conductivity | Solubility in Water |
|---|---|---|---|---|
| X | brittle, white | 800 °C | only if melted/dissolved | soluble |
| Y | shiny, malleable | 1100 °C | high | insoluble |
| Z | hard, colorless | 3550 °C | none | insoluble |
X = ionic; Y = metallic; Z = covalent network
Identify the following substances as ionic, metallic, covalent network, or molecular solids:
Substance A is malleable, ductile, conducts electricity well, and has a melting point of 1135 °C. Substance B is brittle, does not conduct electricity as a solid but does when molten, and has a melting point of 2072 °C. Substance C is very hard, does not conduct electricity, and has a melting point of 3440 °C. Substance D is soft, does not conduct electricity, and has a melting point of 185 °C.
Substance A is shiny, conducts electricity well, and melts at 975 °C. Substance A is likely a(n):
(a) ionic solid
(b) metallic solid
(c) molecular solid
(d) covalent network solid
(b) metallic solid
Substance B is hard, does not conduct electricity, and melts at 1200 °C. Substance B is likely a(n):
(a) ionic solid
(b) metallic solid
(c) molecular solid
(d) covalent network solid
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