1. What do you think are some useful
characteristics of water?
2. How do you think water helps the body
function?
1.
Water
molecules
form
by
A. Water’s
COVALENT BONDS between
Polarity
two hydrogen (H) atoms and
one oxygen (O) atom.
a. Water molecules are
POLAR - one side of the
molecule is positively charged,
while the other is negative.
- Oxygen is negative,
hydrogen is positive.
b. Opposite charges are
attracted to each other.
- HYDROGEN BONDS form
between H of one water
molecule
and O of
another.
B.
1. HYDROGEN BONDS allow
Properties water to have some unique
of
properties.
Water
a. COHESION – water
molecules HYDROGEN BOND to
other
water
molecules.
- COHESION creates
SURFACE TENSION, or solid-like
behavior on the surface of
water.
Ex: Something light can
“sit” on the surface of water.
b. ADHESION – water
molecules hydrogen bond to
molecules of other surfaces.
Ex: Water drops remain in
an “empty”
water
bottle.
C.
Mixtures
with
Water
1. MIXTURE - combination of
two or more substances where
each substance retains its
individual properties.
2. MIXTURES can be either
HOMOGENEOUS or
HETEROGENEOUS.
a. HOMOGENEOUS
MIXTURES are evenly
distributed throughout. They
are also known as SOLUTIONS.
-In a SOLUTION, the
SOLVENT is the liquid into which
something is dissolved.
-The SOLUTE is what is
being
dissolved
in the
SOLVENT.
b. If something dissolves in
water, it is SOLUBLE.
-Only other POLAR
substances dissolve in water.
c. Parts of a
HETEROGENEOUS MIXTURE
remain distinct or separate.
-In a SUSPENSION, particles
separate from the liquid.
3. Water is known as the
“universal SOLVENT” because it
will dissolve many SOLUTES.
a. This is due to water’s
POLARITY.
b. ACIDS - substances that
release H+ when dissolved in
water.
-More H+ = more ACIDIC.
c. BASES - substances that
release hydroxide ions (OH−)
when dissolved in water.
-More OH- = more BASIC.
4. Amount of H+ or OH- ions in
a solution determines the
strength of an ACID or BASE
a. The amount of of H+ in a
solution is called pH.
-ACIDS have pH values < 7;
BASES have pH values > 7
5. Metabolic processes require
a neutral pH (6.5-7.5).
a. BUFFERS - mixtures that
balance the pH of an substance.
-Ex: BUFFERS in our blood
keep the pH at 7.4.