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- [Voiceover] Water
itself is all around us.

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Basically, our life depends on water.

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So a couple things about
water we need to know.

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First off, water molecules are polar.

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But what does that mean?

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Water molecules are two
hydrogen and one oxygen, H2O.

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Because of the way they're arranged,

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with an oxygen molecule in the middle,

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and then two hydrogens on each side,

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gives us H bound to an O bound to an H.

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This gives a polar configuration.

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It means that one portion
is a little more negative,

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while the other portion of the molecule

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is a little more positive.

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Instead of the whole entire molecule

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being positive or negative, it has both,

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a slight polarity on one side,

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a slight positive aspect on one side,

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and a slight negative
aspect on the other side.

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When we have our water
in our body, it's liquid.

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It's kind of a good thing because

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if the water in your body was ice, solid,

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it might be a little
problem moving around.

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If it was vapor, as in gas,

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it could also cause some problems there.

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Water is liquid from
what temp to what temp?

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From roughly 0 degrees Celsius
to 100 degrees Celsius,

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or if you want to look at Fahrenheit, it's

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32 degrees Fahrenheit up
through 212 degrees Fahrenheit.

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That whole range, water
is primarily liquid.

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Now at each end, the high and low end,

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there are little variations depending on

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altitude and a few other
things that go into it.

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But for the most part, it's liquid.

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Water is great at absorbing energy.

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It can absorb energy,
especially heat energy,

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and that's what allows it to warm up.

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When you put a pot of
water on the stove to boil,

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does it boil immediately?

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No.

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It takes the heat energy from the stove,

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takes it into the water,
absorbs it, holds it,

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and gets warmer and warmer.

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Water is just a great way
to hold and store energy.

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Biological solvent.

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Well, a solvent is something
that has other components

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basically dissolving into it.

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Think about salt water.

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You can grab a glass of
water, pour some salt into it.

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The salt will dissolve into the water.

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The water is a solvent.

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Same thing happens inside your body.

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Water allows numerous other molecules

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to dissolve into it.

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Body temp regulation.

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Can you think of a way that water

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helps you regulate your body temperature?

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Now you may have thought
of sweating, sure.

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By sweating, you're releasing water

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that's absorbing heat
energy and then evaporating,

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helping to cool the body down.

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Or if you want the other
way, water holds heat

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and prevents heat from
being lost as quickly.

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So solvent, I already said solvent

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is when something else
can dissolve into it.

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Now we'll put the term liquid there,

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because it's kind of hard to have things

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dissolve into a solid or a gas.

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It's a liquid that has other substances.

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It could be anything that will allow it

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to be dissolved into.

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Salt dissolves into the
solvent water, for example.

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Water is a solvent.

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In that case, the solute
would have been salt.

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The solute is any substance that can

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dissolve into another substance.

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Hydrophilic.

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Well, water is great at being hydrophilic.

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Hydro, the prefix, H-Y-D-R-O,
hydro refers to water.

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The second half, philic, P-H-I-L-I-C,

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philic means love.

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Hydrophilic means water loving.

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Any hydrophilic molecule
is attracted to water.

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It can interact with water.

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Do you think, I don't know,
oil is hydrophilic to water?

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Does the oil easily interact with water?

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Does the oil easily mix with water?

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No, oil and water, they
don't really mix at all.

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So oil would not be hydrophilic.

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Oil would be hydrophobic.

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Hydrophobic are molecules that do not

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want to interact with water.

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They cannot dissolve in water.

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If you pour oil into water,

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I don't care how much you shake it up,

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you get tiny little
droplets of oil on there

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that will slowly start
to group back together

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to eventually form an entire layer of oil

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separate from the water.

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So hydro, water, phobic, fear.

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Hydrophic is water fearing.

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Here's an example showing the
sodium ions and chloride ions.

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You can see that the NA+,

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the little lightly colored,
almost orangish-yellow there,

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and A+ is sodium.

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The green, the CL- is chloride.

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Sodium chloride is salt.

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When sodium chloride is arranged

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in that alternating pattern you see there,

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that forms a salt crystal.

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Put a salt crystal in
water, what will happen?

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The water molecules, which is
the two small blue spheres,

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and a large red sphere.

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Each blue sphere is a hydrogen.

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Each red sphere is oxygen.

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You can see there's two hydrogens

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and one oxygen together.

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What these water molecules will do,

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they will surround each individual sodium

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or chloride ion, slowly
picking the crystal apart,

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slowly allowing the salt
crystal to dissolve.

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But water is not just hydrogen ions.

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It has a few other things going on.

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Those hydrogen ions
that are part of water,

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they can be used to also indicate

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acidic or basic solutions.

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An acid, for instance.

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I bet you guys have probably heard of

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some type of acid.

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Maybe it's hydrochloric
acid, sulfuric acid, nitric.

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There's many different acids out there.

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Acids in general are going
to donate a hydrogen ion.

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What that means is,
they're going to give off

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or give away a hydrogen ion.

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The case of hydrogen and then
chlorine, hydrochloric acid,

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it's one hydrogen and one chlorine.

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In hydrochloric acid,
they can break apart.

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The hydrogen ion is released.

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The more hydrogen ions, the
more acidic a solution becomes.

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Therefore, if you increase
those hydrogen ions,

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then that means you are going towards

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the acidic side of things.

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Well, bases, they're the exact opposite.

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Sodium hydroxide, NAOH, is a great base.

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It accepts hydrogen ion.

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These bases are going to
take the free hydrogen ions,

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the ones just floating around.

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They'll take them and bind them.

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By binding the hydrogen,

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it lowers the hydrogen ion concentration.

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The lower the hydrogen ion concentration,

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the free hydrogen ions,
not the ones bound,

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just the free ones floating around,

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the lower the hydrogen ion concentration,

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the more basic the solution will be.

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These acids and bases, they're
measured on this pH scale.

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The pH scale is based on the
concentration of hydrogen ions.

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The most acidic will have the highest

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concentration of hydrogen ions.

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The most basic, which is
the other side of the scale,

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will have the least
hydrogen ion concentration.

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Here is your pH values, anywhere from 0,

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all the way up to 14.

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Now, the pH of 7, you see it's
right next to the neutral pH.

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That's pretty close
for human blood, tears,

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a lot of bodily fluids.

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Now they're not exactly
7.000, but they're close.

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As you look down into the
reddish area, that more acidic,

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you can see you get numbers decreasing,

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7, 6, 5, 4, 3, 2, 1, 0.

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That's talking about the
concentration of hydrogen ions.

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As you get down to tomatoes,
vinegar, and lemon juice,

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they're all pretty acidic.

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But go up towards that
blue side of things,

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8, 9, 10, 11, 12, 13, 14,

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well those are becoming more basic,

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or more alkaline.

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Baking soda, ammonia,
bleach, drain opener,

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all very basic.

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We have our acidic, high
hydrogen ion concentration,

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basic or alkaline, low
hydrogen ion concentration.

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But your body needs to stay
within a certain range,

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so thankfully we have buffers.

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A buffer is meant to
minimize the pH change.

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Doesn't matter how much acid
or base it is initially.

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It helps it damper or
prevent a very quick change.

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It creates a more stable
environment in the body fluids,

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keeping the pH in a smaller, narrow range.

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For example, your blood
pH typically sits around

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7.35 to 7.45.

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Just a little bit basic.

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Notice it's only a 0.1 difference,

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7.35 to 7.45.

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Your body keeps the blood within that pH.

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It's all because of buffers to minimize

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the change up or down.

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Now, one of the most
prevalent buffering systems

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in the human body is the
carbonic acid bicarbonate system.

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The HCO3- is going to
be your bicarbonates.

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H2CO3 is a carbonic acid.

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If you notice, the carbonic acid

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can donate a hydrogen ion.

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One hydrogen ion is released,

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see how there's a free hydrogen ion,

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and therefore HCO3.

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We have this buffering system,

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carbonic acid bicarbonate.