Download The pH Scale…

pH
What is pH?
pH is the scale that tells you whether a
substance is acidic, basic, or neutral.
pH=“p” stands for power and “H” stands
for hydrogen.
The values correspond to the
concentration of the hydronium ions.
What is an acid?
An acid is a substance that donates
hydrogen ions (H+) to form additional
hydronium ions when dissolved in water.
Therefore, there is a larger concentration
of hydronium ions versus hydroxide ions.
What is the formula for a Hydronium ion?
Just add an H+ to water (H2O)
= H3O+ (hydronium ion)
What is a base?
A base is a substance that either contains
hydroxide ions or reacts with water to form
additional hydroxide ions.
Therefore, there is a larger concentration of
hydroxide ions versus hydronium ions.
What is the formula for a Hydroxide ion?
Just take an H+ from water (H2O)
-
= OH
There’s no HO’s in science! 
Do you remember any compounds that had an OH?
NaOH Sodium Hydroxide from the Penny Lab!
Properties:
ACIDS
BASES
• Sour taste
• Can burn skin
• Contains more
H3O+ than OH-
• Bitter taste
• Can burn skin
• Contains more OHthan H3O+
• Feels slippery/soapy
What is a common property of Acids and Bases?
They both can burn!
The pH Scale…
The pH scale ranges from 0-14.
0 = most acidic
7 = neutral (Distilled H2O)
14 = most basic
But you can also have…
Diluted acids= 3,4,5,6 on the pH scale
and
Diluted bases = 8,9,10,11 on the pH scale!
Diluted vs. Concentrated
• Diluted means to weaken with the
addition of water.
• Concentrated means to strengthen with
the absence of water.
• Think about when you made Kool-Aid and
added too much water and what it
tasted like.
• Too much water = it was too diluted =
Does not taste good!
Copy pH scale in
Notebook
pH Scale
Diluted= weak
Concentrated=strong
During the Lab…
You will find the pH level using the pH probe.
(take one place after the decimal point)
Remember to dip the probe into the clean water
BEFORE you dip it into the chemical!
You will dip it in the substance for about 30 seconds
and record the reading.
You will Clean up any spills. Do not waste time talking.
You will Hold on to the probe when it is in the beaker.
You will Leave the pH probe at the table in the beaker
of water!
You will Move clockwise after 2 minutes / table.
1.
2.
3.
4.
5.
Post-Lab Questions
Which items were the is most acidic?
Which items were the most basic?
Which items on your scale were neutral?
Which items on your scale were weakest acids?
Which items on your scale were the weakest
bases?
6. Why would you take an antacid if your stomach
was upset?
12
7. Label your pH scale with the
different
substances, according to the pH you found!
Copy pH scale in
Notebook
Fill in pH Scale
Acids and Bases
• We can have weak acids and bases. Likewise, we can
have strong acids and bases.
• Neutralize- to add an acid to a basic solution or a
base to an acidic solution until it is chemically
neutral or safe. (pH = 7).
• So…how would you neutralize a strong base like a
laundry detergent spill on your skin?
Pour large amounts of a weak acid on your skin like
vinegar
Very Acidic
Neutral
Very Basic
So what’s wrong with Soda?
• Prolonged exposure to
soft drinks can lead to
significant enamel loss
(tooth decay)!
• The erosive potential of
colas is 10 times that of
fruit juices in just the
first three minutes of
drinking!!!