Geos. 101, Lecture 1 (MWF - Kresan)
Fall 1998, First Exam (50 points)
Multiple Choice (2 points each; 40 points total) – Circle the BEST answer.
1. The chemical bond within an ionic compound is formed by
A. electron sharing.
B. neutron sharing.
C. gain or loss of electrons.
D. gain or loss of protons.
2. What is the smallest unit of an element that retains the chemical and physical properties of that element?
A. Atom.
B. Nucleus.
C. Electron.
D. Proton.
E. Neutron.
3. Quartz is
A. a compound.
B. a mineral.
C. composed of two elements.
D. all of these.
4. The two most abundant elements of the Earth's crust are
A. oxygen and iron.
B. iron and silicon.
C. magnesium and iron.
D. silicon and oxygen.
5. Which of the following statements regarding the scientific method is true?
A. A hypothesis must be agreed upon by more than one scientist.
B. A theory is a hypothesis that has withstood many scientific tests.
C. A theory is proven to be true, and therefore may not be discarded.
D. A hypothesis cannot predict the outcome of scientific experiments.
6. The structure of pyroxene, (Mg,Fe)SiO
3, consist ofA. isolated silica tetrahedra.
B. linked pairs of silica tetrahedra.
C. single chains of silica tetrahedra.
D. double chains of silica tetrahedra.
7. The most abundant class of minerals is the
A. oxides.
B. silicates.
C. carbonates.
D. sulfates.
8. The mantle of the Earth is probably composed of
A. an iron-nickel alloy.
B. silicates rich in iron and magnesium.
C. quartz and feldspars.
D. metamorphic rocks like gneiss and mica schist.
9. Quartz, SiO
2, has which of these structures?A. Isolated tetrahedron.
B. Sheet.
C. Double chain.
D. Three-dimensional framework.
10. Which mineral exhibits no cleavage?
A. Quartz.
B. Mica.
C. Calcite.
D. Graphite.
11. Diamond is an example of what type of bonding?
A. Covalent.
B. Ionic.
C. Metallic.
D. Nuclear.
12. Large crystals with well-formed crystal faces tend to form when
A. molten rock cools quickly.
B. rocks undergo melting.
C. minerals have the space to grow such as in open cavities.
D. volcanoes erupt explosively.
13. Which of the following elements is never found in nature as a pure, native element?
A. Carbon.
B. Copper.
C. Gold.
D. Silicon.
14. Given two minerals with the exact same chemical composition, which mineral is more likely to form at higher pressure?
A. The mineral with the higher hardness.
B. The mineral with the lower hardness.
C. The mineral with the higher density.
D. The mineral with the lower density.
15. Obsidian (volcanic glass) is unusual because
A. of its rare metamorphic origin.
B. it contains no silica.
C. it contains no minerals.
D. it is an evaporite.
E. it is very coarse-grained.
16. Which of the following will contain the most silica?
A. Andesite.
B. Basalt.
C. Fissure eruptions.
D. Rhyolite.
17. Which pair of rocks are associated with high silica content?
A. Basalt and gabbro.
B. Granite and andesite.
C. Ultramafic rocks and rhyolite.
D. Rhyolite and granite.
E. Diorite and andesite.
18. A porphyritic texture is formed
A. by a period of rapid cooling followed by a period of slow cooling.
B. by a period of slow cooling followed by a period of rapid cooling.
C. by the very slow cooling of a water-rich magma.
D. when a magma first crystallizes mafic minerals and then felsic minerals.
19. Which of the following types of rocks form the interior of the Earth?
A. Clastic sedimentary rocks.
B. Biochemical sedimentary rocks.
C. Volcanic igneous rocks.
D. Plutonic igneous rocks.
20. Which type of silicate minerals crystallize at the highest temperature?
A. Double chain silicates.
B. Sheet silicates.
C. Framework silicates.
D. Isolated tetrahedra silicates.
Matching (1 point each; 5 points total)
21. Match the numbered column of terms with the lettered column of terms.
_____ 1. feldspar A. Mineral having one direction of perfect cleavage
_____ 2. mica B. Hardest mineral
_____ 3. Fe, Mg silicate C. Most common mineral
_____ 4. diamond D. Highest density minerals
_____ 5. oxygen E. Most common element
Discussion Question (5 points) – Answer only ONE of the following questions. Be as complete as possible. Use sketches or diagrams to ilustrate your discussion. Continue your answer on the reverse side if more space is needed.
22. Discuss the role of silica tetrahedron in silicate minerals. For full credit your answer must include the following:
A. Number of silica and oxygen atoms in the tetrahedron.
B. Names and arrangements of the tetrahedra for the five silicate structural groups.
C. An example of a mineral or mineral group belonging to each silicate structural group.
23. A. Why does mica exhibit excellent cleavage in one direction? Discuss two factors.
B. How do the two factors discussed in part A explain why the physical properties of graphite and diamond are so different, even though they are both made from 100% carbon?