From the tangy bite of a piece of fruit,
to the caustic liquids used to clear a
clogged sink, acids are a type of
chemical that can be found in many
different aspects of our daily lives, but
what is it about acids that make some
safe to eat and others dangerous? When
talking acids, we're gonna be talking
hydrogen. Not the gas, but rather the
hydrogen ion, H+. This is a hydrogen atom
that has lost its one and only electron.
All acids produce H+ ions when dissolved
in water, but it's how much H+ a specific
acid can produce in water that will
determine whether it can be safely eaten
or not. But how do we conceptualize and
measure H+ concentration. Søren
Sørensen, a Danish chemist, pondered this
question when he worked at the
laboratories of a commercial brewery in
Copenhagen. It was in 1909 that he
developed a method of quantifying
acidity, what is now known as the pH
scale. His scale works by simply
converting the concentration of hydrogen
ions in a solution to a number between 0
and 14. If a chemical is acidic, then its
pH will always be below a 7 on the scale.
The lower the number the higher the
hydrogen ion concentration. The pH scale
is a logarithmic one, meaning that one
unit difference on the scale, say from 3
to 2, means a tenfold difference in H+
concentration. But zero to seven is only
half of the picture. So what about all
these numbers above 7? Substances that
correspond with this half of the scale
are called bases, and they are the
chemical opposites of acids. The 7 on the
scale represents neutral pH—what would
be perfectly pure water. Like acids, bases
are found in chemicals that we encounter
in our everyday lives.
Cleaning products such as ammonia, baking
soda are bases, as are some simple
medicines like milk of magnesia. They're
bitter to the taste and often slippery
to the touch, kind of like soap. Even
though bases are different than acids,
they too can be strong or weak, and a
strong base can be just as dangerous and
corrosive as a strong acid. Chemically,
the difference between acids and bases
is that acids produce hydrogen ions and
bases accept them. In water acids produce
H+ ions and bases produce OH negative
ions. In reactions between acids and
bases, hydrogen ions will react with
hydroxide ions to make water. This type
of chemical reaction is called a
neutralization reaction. Acids and bases
are also very
important in biochemistry. Many
biological processes are sensitive to
the pH of the surroundings, so
controlling acidity in the body is
crucial.
Some biologically important molecules
like amino acids have dual personalities.
They're said to be amphoteric, which
means that they can act as both acids
and bases. An amino acid has a carboxylic
acid group that can produce hydrogen
ions and an amino group that can accept
hydrogen ions. Acids and bases are all
around us and can vary greatly in terms
of their use and their nature, but they
all involve hydrogen ions being passed
around. Thanks for watching. If you would
like to learn more chemistry basics make
sure to check out these other
interesting videos in the series.
