The air that a scuba diver breathes is pressurized to counteract the pressure exerted by
the surrounding water. Under these conditions, excessive amounts of nitrogen dissolves
in bodily fluids, such as blood. If the diver ascends to the surface too rapidly, the
excessive nitrogen bubbles out of the bodily fluidsmuch like carbon dioxide bubbles out
of a soda immediately after its has been opened. This results in a painful and potentially
lethal medical condition known as the bends. Why does breathing a mixture of helium
and oxygen rather than air help divers to avoid getting the bends?
A) Oxygen and helium have stronger attractions for each other than they do for the
blood, so less helium will be dissolved in the blood and to cause the bends.
B) The helium is less soluble in the bodily fluids and so less dissolves for a given
pressure. Upon decompression, there is less helium to “bubble out” and cause potential
harm.
C) The nitrogen in the blood will bind to helium, and so will be exhaled rather than
being stuck in the blood.
D) Helium is a smaller molecule than nitrogen, so when it bubbles out of solution, it is
less painful and less harmful to the body.
Answer:
The idea of uniformitarianism suggests that
A) the natural laws that operate today are different than those that have operated in the
past.
B) sediments are laid down layer upon layer with younger layers always on the top.
C) the processes and natural laws that operate today have been valid throughout
geologic time.
D) all rocks layers are originally uniform.
Answer: