Some minerals are economical to mine at lower concentrations because of their higher value to society and relatively low extraction costs.
Answer the following statement true (T) or false (F)
True
An element like gold can be mined profitably at a much lower concentration factor (0.001%) than aluminum (35%). The different enrichment factors reflect both the value of these resources to society and the energy required to extract them.
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Economic succession is something that occurs when
a. Changing environmental conditions allow certain species to move into an area and replace other species that are no longer favored by the new conditions. b. Investment opportunities change in the stock market. c. Creative destruction causes companies to fail. d. New and more innovative businesses replace older ones that can no longer thrive under changing economic conditions. e. None of these answers.
Why might the following nuclear reaction not be very good for energy production in a fission reactor?
Fe ? 
Si + 
Mg + 3 neutrons
A. The mass of the by-products is too high, and therefore, the energy released will not be high enough. B. The material only produces a few neutrons so the chain reaction will not be very efficient. C. Interatomic attraction between the products will impede the separation of the atoms from the unstable nuclei. D. The products are not the right size to obtain much energy from the missing mass due to the strong nuclear force. E. The reactants are too small to obtain energy from the missing mass due to strong nuclear force.
Although atoms are the smallest unit of an element, relatively few elements can be found in nature as individual atoms. Which of the following elements can be found as individual atoms?
A) hydrogen B) iron C) krypton D) sulfur
Which of the following explains why the gradient wind better approximates the actual wind than the geostrophic wind does?
A. The gradient wind takes friction into account. B. The gradient wind is stronger than the geostrophic wind. C. The gradient wind allows for curved contours. D. The gradient wind is in hydrostatic balance.