1. Acid and Base
Research Biology
Mr. Luis A. Velázquez

2. What is pH ? pH stands for the potential of Hydrogen
Is the concentration of hydrogen in a given substance.
[ ] is the symbol for concentration.
In other words pH is [H+] in a substance.

3. What is the pH scale ? Is a scale that goes from 0 to 14
Any substance above the pH of 7 is consider a base.
Any substance below the pH of 7 is consider a acid.
Any substance at a pH of 7 is not consider an acid or a base.
pH of 7.00 is consider a neutral pH.

4. What is hydrogen ion? Hydrogen is an positive ion. Hydrogen is H+
In terms of pH we use [H+]
Acids have high [H+]
Bases have very low [ H+ ]

5. What is hydroxide ? Hydroxide is an negative ion. Hydroxide is OH-
In terms of pH we use [OH-]
Acids have low [OH-]
Bases have very high [OH-]

6. pH Scale in terms of [H+]7 14
Base
Acids

7. pH Scale in terms of [OH-]7 14
Base
Acids

8. pH Scale Neutral [ OH-] [ H+] [ H+] [ OH-] Base Acids H2O Equilibrium7 14
[ H+]=
[ OH-]
Base
Acids
H2O
Equilibrium

9. Some important pH A C I D S B A S E

10. Problem Sea water has a pH of 8.50
If a substance x has more [H+] than sea water.
Sea water
8.5
pH more than
pH less than
Down [H+]
Up [H+]

11. Important information
pH for any living thing is between and 7.50
Blood has a constant pH of 7.4
If the pH goes up to 7.5 your blood will become more alkaline or basic. (basidosis)
If your bloods pH goes down you blood will become more acids. ( Acidosis)

12. What is an acid ? An acid pH is to have a number below 7.00.
The smaller the number the more acidic is the substance.
Acids have very high [H+]
Acids have very low [OH-]

13. What is base ? A basic or alkaline pH is to have a number above 7.00.
The greater the number the more alkaline is the substance.
Bases have very low [H+]
Bases have very high [OH-]

14. Stronger and weaker acid

15. Understanding Cabbage
The purple color in red cabbage comes from a class of pigment molecules called anthocyanins.
It turns out that anthocyanins are found in flower petals, leaves (it makes them turn red in the fall!) and some fruits such as blueberries.
Anthocyanins are plant pigments known as flavenoids and produce red, pink, violet and magenta colors in the various plant parts.

16. Cabbage Lab The anthocyanin turns into: bright pink in acids
reddish-purple in neutral solutions
green in alkaline or basic solutions.

17. Cabbage Lab
This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and grapes.
Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in red cabbage juice.

18. Cabbage Lab Analysis pH 2 4 6 8 10 12 Color Red Pink Violet Blue
Blue-Green
Greenish Yellow

19. What are buffers?
A substance that eliminates large sudden changes in pH.
Buffers help organisms maintain the pH of body fluids within the narrow range necessary for life.
Are combinations of H+ acceptors and donors forms in a solution of weak acids or bases
Work by accepting H+ from solutions when they are in excess and by donating H+ when they have been depleted.

23. Acids and Bases
An acid is a substance that increases the hydrogen ion concentration in a solution.
Any substance that reduces the hydrogen ion concentration in a solution is a base.
Some bases reduce H+ directly by accepting hydrogen ions.
Strong acids and bases complete dissociate in water.
Weak acids and bases dissociate only partially and reversibly.
There is only 1 molecule out of 554,000,000 water molecules that is dissociated.

24. Classify the following pH
A = Acid
B = Base
N = Neutral
A ____
B ____
C ____
D ____
E ____
F ____
G ____
H ____
I ____
J ____
K ____
L ____
M ____
1. How many acids?_______
2. How many bases?_______
3. Who is the weakest base? ___
4. Who is the strongest acid? ___
5. Who is the weakest acid? ___
6. Who is the strongest base? ___