Why is oxygen the most common element in Earth's crust, but not in Earth as a whole?
What will be an ideal response?
Density segregation- dense elements sank to earth's center and lighter elements rose to the surfcae
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The average kinetic energy of a nitrogen molecule at room temperature (20°C) is
a. 2 × 10^?21 J. b. 4 × 10^?21 J. c. 6 × 10^?21 J. d. 8 × 10^?21 J. e. 1 × 10^?20 J.
Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit. Which of the following best describes what the planets would look like?
A) The planets are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the rest planets are spread much farther apart. B) The planets are all much smaller than the Sun and are spread out evenly over a distance about the length of a large classroom. C) The planets are all much smaller than the Sun. Four planets are located within a few centimeters of the Sun, and four planets are located at distances ranging up to about a meter. D) The planets range in size from about the size of a marble to the size of a baseball. They are spread out over a region about the size of a football field.
The number of protons in a neutral atom is balanced by an equal number of
A) electron shells that surround the nucleus. B) neutrons in the nucleus. C) orbital electrons. D) none of the above
Which of the following is NOT one of the four stages in the development of a terrestrial planet?
a. flooding b. cratering c. slow surface evolution d. fusion of hydrogen to helium e. differentiation