The wave speed of sound waves traveling through four different media was measured at a constant temperature. Results are summarized in the table. Which statement provides a plausible hypothesis based on these results?
Medium Wave Speed of Sound
Cork 366 m/s
Water 1,433 m/s
Glass 5,640 m/s
Steel 6,100 m/s

A.
Changing the composition of a medium from metals to nonmetals enables sound waves to be transmitted at higher speeds.
B.
Changing the state of a medium from liquid to solid enables sound waves to be transmitted at higher speeds.
C.
Decreasing the brittleness of a medium enables sound waves to be transmitted at higher speeds.
D.
Increasing the density of molecules in a medium enables sound waves to be transmitted at higher speeds.

The particle in a two-dimensional well is a useful model for the motion of electrons around the indole ring (3), the conjugated cycle found in the side chain of tryptophan. we may regard indole as a rectangle with sides of length 280 pm and 450 pm, with 10 electrons in the conjugated p system. as in case study 9.1, we assume that in the ground state of the molecule each quantized level is occupied by two electrons. (a) calculate the energy of an electron in the highest occupied level. (b) calculate the frequency of radiation that can induce a transition between the highest occupied and lowest unoccupied levels. 9.27 electrons around the porphine ring (4), the conjugated macrocycle that forms the structural basis of the heme group and the chlorophylls. we may treat the group as a circular ring of radius 440 pm, with 20 electrons in the conjugated system moving along the perimeter of the ring. as in exercise 9.26, assume that in the ground state of the molecule quantized each level is occupied by two electrons. (a) calculate the energy and angular momentum of an electron in the highest occupied level. (b) calculate the frequency of radiation that can induce a transition between the highest occupied and lowest unoccupied levels.

If an atom contains 11 protons in its nucleus, predict the element with the atomic number and electronic configuration. will the number of electrons remain the same during the chemical reaction in such an atom? explain.

When the displacement of a mass on a spring is 12a the half of the amplitude, what fraction of the mechanical energy is kinetic energy? at what displacement, as a fraction of a, is the mechanical energy half kinetic and half potential?