1. Introduction: Sketch the pH scale
Solutions and pH
Introduction: Sketch the pH scale

2. Solutions & Suspensions
Water is usually part of a mixture.
There are two types of mixtures:
Solutions
Suspensions

3. Water is the solvent of Life!
Properties of Water
Universal Solvent
Water is the solvent of Life!
Solute – substance dissolved in a solvent to form a solution
Solvent – fluid that dissolves solutes
Example: Ice Tea – water is the solvent and tea and sugar the solutes

4. Solution Ionic compounds disperse as ions in water Evenly distributed
SOLUTE
Substance that is being dissolved
SOLVENT
Substance into which the solute dissolves

5. Solution

6. Suspensions
Substances that don’t dissolve but separate into tiny pieces.
Water keeps the pieces suspended so they don’t settle out.

7. Acids, Bases and pH H2O  H+ + OH-
One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-)
Hydrogen Ion Hydroxide Ion
Acid Base
H2O  H+ + OH-

8. The pH Scale Indicates the concentration of H+ ions Ranges from 0 – 14
pH of 7 is neutral
pH 0 up to 7 is acid … H+
pH above 7 – 14 is basic… OH-
Each pH unit represents a factor of 10X change in concentration
pH 3 is 10 x 10 x 10 (1000) stronger than a pH of 6

9. Acids and Bases
Strength compared using pH scale
Ranges from 0 – 14
Logarithmic Scale (gets 10x bigger/smaller)
Acid – donates H+ when added to aqueous solutions
Ranges from pH 0-6.9
Base – breaks up into hydroxide (OH-) ions and
another compound when placed in an aqueous
solution
Ranges from pH 7.1 – 14
Distilled water is pH 7.0 or neutral. Why?
H2O H OH-

10. Acids:
 Bases:
Taste sour.
 Taste bitter.
Give sharp stinging pain in a cut or wound.
 Feels slippery
Turn blue litmus paper red.
 Turn red litmus paper blue.
Turn phenolphthalein colorless.
 Turn phenolphthalein pink.
React with metals to produce hydrogen gas.
React with carbonates or bicarbonates to produce carbon dioxide gas.

12. Acids
Strong Acids have a pH of 1-3
Produce lots of H+ ions

13. Bases Strong Bases have a pH of 11 to 14
Contain lots of OH-ions and fewer H+ ions

14. Buffers
Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH (neutralization).
Produced naturally by the body to maintain homeostasis
Weak Acid
Weak Base

15. Acids and Bases
Buffers – compounds used to maintain a contant pH within a system
H2CO3 H HCO3-
Carbonic acid bicarbonate ion

16. Acids and Bases

17. Making Biological Molecules
and H2O
Condensation Reaction
H2O
Hydrolysis Reaction

18. Practice
When most people think of chemistry the first terms that come to mind are acids and bases. Many of the chemicals that people run across have some connection to acids and bases. For instance many people take medicine every day to cure heart burn. These medicines are (acids/bases). One of these comes in a blue bottle and is known as “Dr. MOM”. The common name for this is Milk Of Magnesia Another product claims that it is better for us to use because it contains calcium. So in addition to helping relieve the heartburn, it also provides us with needed calcium. This product is called Tums and its chemical name is __________________.

19. Practice
Another product that is used all the time is Draino. Draino is a(n) (acid/base) and it has the common name of “lye” the chemical name is _____________________, and the chemical formula is ___________________. This chemical is more dangerous than the ones used for heartburn and can cause blindness or burns. (Acids/Bases) are also commonly used to produce soaps and have a (bitter/sour) taste.

20. Practice
Seltzer water and all sodas contain a very mild (acid/base) known as _____________________. This is formed by dissolving carbon dioxide in water. The chemical formula for this substance is ___________________. Vinegar is a(n) (acid/base) finds its way into our diet in ketchup and most salad dressings. The chemical name for vinegar is , the chemical formula for this substance is ___________________.

21. Homework
Keep track of what you eat today and determine which are acids and bases
Bring things in from home that you would like to test for pH

22. Application Why is it important to know about pH in Biology?
What happens to pH of solutions in your body when you don’t drink enough?
What happens to pH of solutions in your body when you eat to many sour foods?