Pure water is a colorless, odorless liquid with no molecules
except H₂O in it. You can buy it at the supermarket, or make
it at home if you have the equipment and know how to use it.
At the supermarket, it's sold in gallon jugs, marked "Distilled
Water".
It turns out that pure water tastes bleah, and you would not
want to drink it for very long.
The Earth's water cycle is constantly purifying our water.
When the sun warms the ocean's surface and evaporates
water, what evaporates and rises into the atmosphere is
pure water. The pollutants don't evaporate. The clouds,
the rain, and the rivers are self-purifying. Another example
of a process of nature that makes life possible here.
The junk is collecting in the oceans. We're lucky that the oceans
have such huge volume that we haven't been able to significantly
pollute that entire layer of the Earth and kill off all sea life yet.
But we're working on it.
It has changed because earlier in the days people couldn't even figure out if the world was flat or round but now we can add decimals and multiply fractions.
A. At the top. At this point, the child is highest, and they are not moving. Their potential energy is much greater.
The
half-life of this radioactive isotope is 9 months for it decreases to
one-fourth its original amount in 18 months. Half-life means a certain length
of time after which half of the amount of radioactive element has decayed.
Therefore,
the half-life of this particular isotope is 18 months. After 18 months the
isotope was at one-half, then another 18 months, the isotope was at one-fourth,
which is 9 months where one-fourth is one-half of one half.
