The pH Scale Is a substance an acid or a base?

ACIDS AAAAn acid is a compound that increases the number of hydrogen ions when dissolved in water (H+) AAAAn acid solution tastes sour AAAAn acid can change the color of certain compounds

What is an ion? **An ion is an atom that has lost or gained an electron giving it a positive (+) or negative (-) charge. ** Charged Atom

USES OF ACIDS  Citric acid and ascorbic acid (Vitamin C) are found in orange juice  Carbonic acid and phosphoric acid give a “bite” to soft drinks  Acids in your stomach aid in digestion  Sulfuric acid is the most widely used industrial acid in the world. It is used in making metals, paper, paints, and fertilizers.

BASES  A base is any compound that increases the number of hydroxide ions (OH-) when mixed with water  A base solution tastes bitter  A base solution feels slippery  A base can change the color of certain compounds

Uses of Bases  Bases are used in soaps (remember, bases are slippery)  Bases are used to make paper, in oven cleaners, and to unclog drains  Ammonia is a base and is used in many household cleaners

Detecting Acids and Bases  You can detect an acid using an indicator.  INDICATOR - A substance that changes color in the presence of an acid or a base.

INDICATORS  Litmus paper is an indicator  An acid turns blue litmus paper red  A base turns red litmus paper blue

pH Scale Acid Base Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 515 [H + ] pH M NaOH Ammonia (household cleaner) Blood Pure wate Milk Vinegar Lemon juice Stomach acid 1 M HCl Acidic Neutral Basic

pH of Common Substances Timberlake, Chemistry 7 th Edition, page 335

Did we Miss something??  What happens when the pH of a substance is 7?  Ans: A pH level of 7 indicates a Neutral Substance i.e: Water!

Why Learn about pH?  What do you think is the pH level of NYC tap water?  The pH of a swimming pool must be checked periodically. Why?  Is it important for Lakes & Rivers to maintain a certain pH?

How do Antacids Work?  Normal pH in your stomach is 3  If your stomach pH drops below 3 you don’t feel so well  An antacid neutralizes the acid in your stomach and brings the pH up to a 3 or 4

Antacids  A base can't neutralize your acid all by itself.  A base needs some chemical "helpers”  All antacids contain at least one of these four primary ingredients:  * Sodium  * Calcium  * Magnesium  * Aluminum.

HOW DO WE MEASURE pH?

A CID B ASE NEUTRALNEUTRAL The pH Scale

A CID B ASE NEUTRALNEUTRAL The pH Scale

Let’s see what you’ve learned!  Professor Know-It- All wants to know what you’ve learned. Answer the following questions carefully.

Question #1  Lemon juice has a pH of 2.2. Is it an acid or a base?

Question #2  Detergents such as Tide have a pH of about 10. Is Tide an acid or a base?

Question #3  Seawater has a pH of 8.2. Is seawater an acid or a base?

Question #4  The inside of your mouth has a pH of 7. Is it an acid or a base?

Question #5  How do you think we came up with the term “acid rain”?

Question #6  409 cleaner contains ammonia that has a pH of 12. What will 409 do to red litmus paper?

Question #7 Question #7  A soft drink has a pH of 3.2. What will it do to a piece of red litmus paper?