Which of the following is considered a chemical
change?
a)boiling
b)dissolving
c)crushing
d)rusting
d
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The 1986 Susan Solomon expedition
A) discovered that the sun's infrared is significantly absorbed by carbon dioxide. B) confirmed that fossil fuels are causing global warming. C) discovered that solar radiation is most energetic at the frequency of yellow-green light. D) confirmed that rain-forest destruction is a significant contributor to ozone depletion. E) confirmed that CFCs are causing ozone depletion over Antarctica.
Which would you expect to have a higher melting point: sodium chloride, NaCl, or aluminum oxide, Image?
A) The aluminum oxide has a higher melting point because it is a larger molecule and has a greater number of molecular interactions. B) NaCl has a higher melting point because it is a solid at room temperature. C) The aluminum oxide has a higher melting point because of the greater charges of the ions, and hence the greater force of attractions between them. D) The aluminum oxide has a higher melting point because of the covalent bonds within the molecule.
Electric Field Lines: Two stationary point charges q1 and q2 are shown in the figure along with a sketch of some field lines representing the electric field produced by them. What can you deduce from the sketch?
A. q1 is negative and q2 is positive; the magnitudes are equal. B. q1 and q2 have the same sign; the magnitudes are equal. C. q1 is positive and q2 is negative; the magnitude of q1 is greater than the magnitude of q2. D. q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2. E. q1 and q2 have the same sign; the magnitude of q1 is greater than the magnitude of q2.
RC Circuits: A 2.0-?F capacitor is charged to 12 V and then discharged through a 4.0-M? resistor. How long will it take for the voltage across the capacitor to drop to 3.0 V?
A. 8.0 s B. 11 s C. 22 s D. 24 s