For an exothermic reaction, the energy barrier is ______________ on the reactant side than on the product side
a. smaller
b. not different in size
c. greater
a
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Convection is important in stars because it
a. increases the temperature of the star. b. mixes the gases of the star. c. transports energy outward in the star. d. carries the neutrinos to the surface of the star where they can escape. e. b and c
Observationally, a key distinction between a white dwarf supernova and a massive-star supernova is that the spectrum of a massive-star supernova shows prominent hydrogen lines, while the spectrum of a white dwarf supernova does not. Why don't we see prominent hydrogen lines in the spectrum of a white dwarf supernova?
A) White dwarf supernovae occur so far away that their hydrogen lines become too dim to see. B) During a white dwarf supernova, all the white dwarf's hydrogen fuses instantly to make helium. C) White dwarfs are stellar corpses that contain little or no hydrogen, so they do not show hydrogen lines when they explode. D) The hydrogen lines of white dwarf supernovae are so redshifted that we cannot detect them.
A beaker is filled to the 500 ml mark with alcohol. What increase in volume (in ml) does the beaker contain when the temperature changes from 5° C to 30° C? (Neglect the expansion of the beaker, evaporation of alcohol and absorption of water vapor by alcohol.) ?alcohol = 1.12 × 10^?4/°C
a. 0.47 b. 0.93 c. 1.4 d. 1.7 e. 2.5
When a negative charge is released and moves along an electric field line, it moves to a position of
a. lower potential and lower potential energy. b. lower potential and higher potential energy. c. higher potential and lower potential energy. d. higher potential and higher potential energy. e. decreasing magnitude of the electric field.