2. Water
• Water is an inorganic Molecule
– TO BE ORGANIC, A MOLECULE MUST
HAVE CARBON IN IT
– What is the Chemical Formula for Water?
– So, it can’t be organic!
3. What is weird about water?
Remember Polarity?
• We did the “pom-pom” lab an learned
that some molecules are not linear
• Water has opposite charges at opposite
ends
This gives water several
unique properties
4. Water molecules display
Polarity
And this Polarity causes:
Cohesion &
Adhesion &
Surface Tension
(Remember? We learned about the meniscus in
a test tube)
5. Cohesion – Water molecules stick to
each other
Adhesion – Water molecules stick to
other molecules
Surface Tension – The “tension” (almost
like a film) on the surface of water
caused by cohesion
Meniscus – The “curve” at the top
surface of water in a graduated cylinder
caused by adhesion
6. Dissociates
• Water is made up of two different
elements
– 2 atoms of Hydrogen
– 1 atom of Oxygen
• When water dissociates (breaks apart)
it forms two different ions
• Hydroxide (-OH)
• Hydrogen (+H)
– An ion is a molecule that has a charge
• Can be positive or negative
7. Swimming Pools
• Ever open your eyes in a swimming pool
and they end up red and burning?
8. Heartburn?
• Have you ever
had heartburn?
– Sometimes
called Gerd
• It feels like
your heart is on
fire
• It is caused by
stomach acid
“climbing up”
your esophagus
9. How do you get rid of it?
• Since heartburn
is caused by
stomach acid
climbing up the
esophagus…
• You neutralize
it with
“antacids”
• Which are
basic!
10. Acids & Bases are Based on
WATER!
• Depending on the amount of H+ or OH-
ions, the “water” becomes either acidic
or basic (aka alkaline)
• The pH scale determines the strength
of the acid/base
• The pH scale runs from 0 -14
– Low numbers are acidic
– High numbers are alkaline
– “7” is neutral Water
12. pH scale
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
ACID BASE
NEUTRAL
Each step on pH scale represents a factor of 10
pH 5 vs. pH 6 (pH 5 is 10X more acidic)
pH 8 vs. pH 13 (5 steps = 10x10x10x10x10 = 100,000X difference)
measures acidity/basicity
10x
10x10x
100x
Søren Sorensen
(1868 - 1939)
pH 3 vs. pH 5 (2 steps = 10x10 = 100X difference)
13. Characteristics of Acids
Taste Sour
Conduct Electricity
Corrosive, which means they break down
certain substances. Many acids can
corrode fabric, skin and wood
Some acids react strongly with metals
Turns blue litmus paper red
Turn pH Paper Yellow Red
Depending on strength of acid
14. Characteristics of Bases
aka - Alkalis
Feel Slippery (Think SOAP!)
Taste Bitter
Corrosive (Just as corrosive as Acids!)
Can conduct electricity. (Think alkaline
batteries.)
Do not react with metals
Turns red litmus paper blue
Turn pH paper Green Blue
Turn Phenolphthalein Pink
15. Acids/Bases
• The lower the pH, the stronger the acid
• The higher the pH, the stronger the
base
• Did you know the human body produces
BUFFERS to maintain homeostasis
– Buffers help to neutralize acids and bases
16. Acid – Base Reactions
A reaction
between an acid
and a base is
called
neutralization.
An acid-base
mixture is not as
acidic or basic
as the individual
starting
solutions.
17. Acid – Base reactions
Acid + Base = Salt +
Water!
Each salt listed in
this table can be
formed by the
reaction between an
acid and a base.
Neutralization
18. Neutralization
• To neutralize (counter-act) an acid, you
add a base
• To neutralize (counter-act) a base, you
add an acid
• The Buffers your body produces are
either acidic or basic...
19. Buffers
• A buffer is a solution the helps return
another solution to its proper pH
• A buffer can “soak up” excess H+ ions
(acid) or “soak up” excess OH- ions
(base)
• Your body produces buffers ALL THE
TIME in order to maintain homeostasis
– Think about all of the acidic stuff you eat!
20. 20
• Most living organisms
have a very narrow range
of tolerance for pH
• Remember…Each pH unit
represents a factor of 10
difference in [H+]
• How do we figure out
what’s an acid and what’s a
base?
LITMUS or pH PAPER!
The pH scale goes from 0 to 14—because [H+][OH-] = 10-14
pH
10-2
10-3
10-5
10-4
10-8
10-7
10-6
[H+] M
10-10
10-9
10-11
10-12
10-13
10-14
10-1
100 A strong acid
A strong base
SOURCE: http://en.wikipedia.org/wiki/Image:PH_scale.png#file
21. pH Paper
• An indicator for pH
• Turns different
colors in different
solutions
– Acid Red
– Base (Alkali) Blue
– Neutral Lt. Green
22. Let’s Try It Out!
• We will be using Litmus paper to
determine the pH of several household
items!
