MDA 125: Earth History

Name _________________________

Exam I: October 4, 1996

Total Points = 54

I. Quickies: Fill in the blank spaces with the word, number, or phrase that is most appropriate. Give units where necessary. (1 point for each blank)

a) The force holding neutrons and protons in the nucleus in called the ______________.

b) The valence is the number of ________________ given up or gained as atoms attempt to _____________________________.

c) Similarities in the behaviors of various elements led to their placement in the _________________________ that is used to classify all chemical elements.

d) Galactic velocity can be determined from _______________________.

e) One way in which distance of objects in the sky can be found is from ___________________________________ (give an approach).

f) The mass of a planet or star can be determined if it has _____________________.

g) The lifetime of a star depends on its _______________. Name a galaxy ___________.

h) As an object is heated, two characteristics of the radiation it emits change:

______________________________ and _____________________________________.

i) Formation of our solar system is thought to include the following steps: A dust cloud collapses because _____________________________________. As it collapses, it begins to spin rapidly in order to conserve ___________________________. The inner planets are ________________________ than the outer planets because ____________________________________________. What evidence exists that earth material was once part of another star? ____________________________________.

j) A statement is called a scientific law if __________________________. One example is the first law of thermodynamics that says _________________________________.

k) During fusion, the mass of the products is always ____________(choose less or more) than the mass of the starting materials. The difference is called the __________________.

II. Matching: Fill in the blanks shown in the left column below with the letter of the phrase in the right hand column of choices that is most appropriate. A letter may be used more than once. (1 point for each blank)

  ____ H A. The most stable form of matter
 ____ He  B. Is "burned" in the core of red giants
 ____ C   C. Shows a valence of +5
 ____ Si  D. Is the daughter product of a radioactive parent
 ____ 56Fe   E. The most abundant form of matter
 ____ 206Pb   F. Has 6 protons in nucleus
   G. A radioisotope useful for age dating
   H. "Burns" explosively

III. Graphs: Draw graphs that show the following. Be sure to label each axis and note whether the scale is linear or logarithmic (6 points each)

a) The Hubble plot for receding galaxies. Briefly explain how this graph can be used to estimate the age of the universe.

 

 

 

 

 

 

 

b) Draw a Hertzsprung-Russell diagram and indicate the positions of main sequence stars, red giants, white dwarfs, supergiants, and our sun. Use a line with arrows to show how a star of solar mass evolves on this diagram.

 

 

 

 

 

 

 

c) Draw a diagram indicating the intensity of background radiation in the universe vs. wavelength. Briefly explain the significance of this discovery.

 

 

 

 

 

 

 

 

IV. Puzzlers: Briefly explain each of the following. You may wish to cite an observation or an equation to explain your answer, although this may not be necessary for some questions. (2 points each)

a) Why is a mass of at least 0.1 solar masses necessary for a star to form?

 

 

 

 

 

b) What factors are important in determining the gravitational attraction between two objects? Use an equation to indicate how they are important. Be sure to define terms.

 

 

 

 

 

 

c) Last night, a mysterious greenish flash was observed in the northeastern sky. A few other colors were observed in this event, as well. There have been some suggestions that this might have been caused by the entry of some satellite debris into our atmosphere, or perhaps a meteorite. Recalling our discussions about spectroscopy, does this seem like a reasonable explanation, and if so, why might the color be green?

 

 

 

 

 

 

d) When sodium has a charge of +1 and chlorine has a charge of -1, they can bond together to form the mineral halite. The nuclei of these two atoms have opposite charges and are attracted toward each other to form an ionic bond, but the nuclei are still far apart in the crystal. Why doesn't the mineral formed shrink further?

 

 

 

 

 

e) A mineral is found to have 25 atoms of 235U and 75 atoms of its stable daughter 207Pb. If no Pb was present when the mineral formed and the half-life of 235U is 0.7 by, estimate the age of the mineral.