An amount of water has a
radioactive gas dissolved in it. Which of the following would
produce a greater contamination risk? (A) Freezing the water. (B) Boiling the water.
Okay, so here we have a container
with this water in it. And we’re told that this water has
a radioactive gas dissolved in it. Now, if the gas was really
dissolved, the little pockets of gas would be so small we couldn’t see them. Here, we’ll represent this gas
dissolved in the water using these dots. We want to know whether freezing
this water or boiling it would produce a greater contamination risk. Let’s remember that contamination
involves the mixing of substances together.
So, for example, if our water, with
gas dissolved in it, were to mix with the air in the atmosphere, that would be
contamination. Or if it mixed with — say, the soil
in the ground — that would be contamination too. So, the way to decrease
contamination risk is to make it hard for this water to mix with any other
substance. We know if the water is frozen, it
will become a solid object. That way, it will be relatively
difficult for the block of ice to mix with any other substance.
But then, let’s think about boiling
the water with the radioactive gas. In that case, everything in the
water, including the radioactive gas, would be released into the atmosphere. Thanks to currents of air, this
material could be spread long distances. So, while freezing the water
contains contamination risk, boiling it makes it more likely that those water and
radioactive gas will mix with other substances. We choose answer option (B).