Acids and bases are everywhere.
They're used to make foods,
soaps and detergents,
fertilizers,
explosives,
dyes,
plastics,
pesticides,
even paper.
Our stomachs are very acidic.
Our blood is slightly basic.
Our proteins are made up of amino acids,
and the letters in our genetic code,
those As, Ts, Cs, and Gs,
are all bases.
You were probably taught
how acids and bases behave
on the molecular level.
You were probably never taught
that a long time ago,
like ancient Greek ago,
before anyone knew about atoms or molecules,
acids and bases were defined
by how they behaved.
Acids tasted sour and corroded metal.
Bases felt slippery
and could somehow counteract acids.
When molecules dissolved in water interact,
they are exchanging two main currencies
with their surroundings:
protons, also known as hydrogen ions,
and electrons.
Depending on how a molecule is composed or shaped,
it may be willing to donate or accept
either protons or electrons
with some other community member.
And some molecules are far more aggressive than others
when it comes to donating or accepting either currency.
Remember that protons are positively charged
and electrons are negatively charged.
So, if a molecule is willing to give up a proton,
that's not too different
from it being willing to accept an electron --
either way it's becoming more negatively charged.
Other molecules are willing to accept a proton
or give up an electron.
These are becoming more positively charged.
Some substances are so aggressive
about donating their protons
that when they get a chance,
all of the molecules in a sample
will dump a proton,
sometimes more than one,
to the surrounding water molecules.
We call these strong acids.
Meanwhile, some compounds are so ready
to accept a proton
that they won't wait around,
they'll just rip one off water,
which usually has two protons
but is generous enough to hang out with just one.
We call these strong bases.
Other acids and bases are not so strong.
They may donate just a few of their protons to water
or accept just a few protons from water,
but most of their molecules stay exactly the same.
If left alone in water,
they'll reach some equilibrium point
where maybe only one out of a hundred
or one out of ten thousand of their molecules
has exchanged currency with water.
As you might guess,
we label these acids and bases weak,
but in the common sense of the word,
they're not weak.
The vinegar in your salad dressing
that you can smell from across the room,
that is a weak acid.
The ammonia you spray on glass
for a streak-free shine,
that is a weak base.
So, it doesn't take much to be an active player
in the chemical economy.
Most acid-base chemistry takes place in water,
which can act as either an acid or a base,
accepting deposits and enabling withdrawals
like a 24-hour molecular ATM.
And when a proton-deposit customer,
that's an acid,
and a proton-withdrawal customer,
the base,
shop at the same time,
their net effect on water's account
may cancel out,
and we call this neutralization.
Now, certain molecules can behave
as acids or bases without water,
but that's another story.
Let's end by saluting water
as the resilient and fair banker
for acids and bases.
It's always open for business,
doesn't charge interest,
and will never foreclose on your molecules,
which is more than I can say for [bleep].
Waah-waah.