Liquid water cannot exist for very long on the surface of Mars today because
A) it gets rapidly destroyed by intense solar radiation
B) its surface temperature is too high
C) it rapidly reacts with the Martian surface to form peroxides
D) its atmosphere is too thin
D
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Two phases ? and ? are in equilibrium, and they are made of A-type and B-type atoms. Which of the following statements is true?
(a) The Gibbs free energies of the ? and ? phases are equal. (b) The chemical potentials of the A-type atoms in the ? and ? phases are equal. (c) The Gibbs free energies of the ? and ? phases are equal to 0. (d) The chemical potentials of the A-type and B-type atoms in the ?-phase are equal.
Which of the following happens when a star runs out of hydrogen at its center?
A) The core of the star expands. B) The outer layers of the star heat up. C) The star moves toward the lower left in the Hertzsprung-Russell diagram. D) The stellar core becomes almost pure helium
Radioactivity Basics: The atom 
Fr decays to 
Ra by emitting what kind of nuclear radiation?
A. alpha B. beta-minus C. beta-plus D. gamma E. x-rays
The diagram is of a simple spectroscope. If lens #1 were omitted, the resulting spectrum would be
1) much dimmer. 2) upside down. 3) no different. If, instead, the slit were opened too wide, the middle of the spectrum would appear 4) white. 5) much narrower. 6) black. 7) a broader yellow.