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May 21 , 2012

May 21 , 2012. AGENDA: 1 – Bell Ringer & Part. Log 2 – CN: Acids & Bases 3 – pH Practice Questions 4 – Summary & Questions. Today’s Goal: Students will be able to compare and contrast acids and bases. Homework Complete summary and questions based on notes.

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May 21 , 2012

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  1. May 21, 2012 AGENDA: 1 – Bell Ringer & Part. Log 2 – CN: Acids & Bases 3 – pH Practice Questions 4 – Summary & Questions Today’s Goal: Students will be able to compare and contrast acids and bases. Homework • Complete summary and questions based on notes. • Week 35 work is due by Friday.

  2. Topic: Acids and BasesDate: 5/21/2012 • Cornell Notes Agenda: • Working Definition of Acids / Bases • Sources of Acids and Bases • How to Determine if something is Acidic or Basic • Common Properties of Acids and Bases • Auto-ionization of water • Acid / Base Strengths – The pH Scale

  3. Acids – Where found? • Acid comes directly from the Latin acidus, which means sour. • Acids flavor many foods and beverages • Meat, poultry and fish are innately acidic, but become more acidic when cooked. • Fruitssuch as citruses, cranberries and tomatoes are acidic. • Acids also help you to digest foods • Gastric Acid (Hydrochloric Acid and other digestive enzymes).

  4. Acids - Definition * • An Acid is any chemical compound that dissociates in solution (dissolves in water), releasing hydrogen ions (H+)or hydronium ions (H3O+). • This results in lowering the solution’s pH (potential hydrogen).

  5. Stop & Think about it! • If an Acid is any compound that yields hydrogen ions (H+) or hydronium ions (H3O+) when dissolved in water… • What is a Base?

  6. Base – Definition * • A Base is any compound that yields hydroxide ions (OH-) when dissolved in water. • Considered to be the chemical opposite of Acids. • In Foods: typically vegetables and some non-sweet fruits. Have a bitter taste. • Bases can be highly caustic(can cause burning, can be corrosive or be destructive to living tissues).

  7. Acid or Base * • The relative amounts of two ions determine whether a solution is acidic (an acid) or basic (a base). An Acidic solution contains more hydrogen or hydronium ions. A Basic solution contains more hydroxide ions.

  8. Auto-ionization of Water * Pure water produces an equal number of hydrogen ions (H+) andhydroxide ions (OH-): H2O (l) H+ion (aq)+ OH- ion (aq) 2H2O (l) H3O+ion (aq) + OH- ion (aq) (hydronium ion)

  9. Acid / Base Properties * • Properties of Acids- Taste sour • Change litmus (a blue vegetable dye) from blue to red • Conduct electric current • React with bases to form salts and water • Examples of Common AcidsCitric Acid (lemons), • Ascorbic Acid (vitamin C), Acetic Acid (vinegar), • Carbonic Acid (soft drinks), • Lactic Acid (in buttermilk) • Properties of Bases- Taste bitter • Change red (acidified) litmus back to blue • Conduct electric current • React with acids to form salts and water • Examples of Common BasesDetergents, Soap, • Lye (NaOH), • Household Ammonia

  10. Acid / Base Strength: The pH Scale * • The pH scale measures how acidic or basic a substance is. • The pH scale ranges from 0 to 14. • A pH of 7 is neutral. • A pH less than 7 is acidic. • A pH greater than 7 is basic. • Mixing acids and bases can cancel out or neutralize their extreme effects.

  11. Acid / Base Strength: The pH Scale * Using the diagram, answer the following: The lower the pH the more “__________”. The higher the pH the more “__________”.

  12. What you know about your body: Which is Acidic and Basic? PRACTICE PROBLEMS: Label each of the following as either: ACIDIC, BASIC, OR NEUTRAL. • Human blood - pH of 7.4. • Note: (If pH of Human blood falls below 7.35, can affect your central nervous system and lead to a coma). • Human saliva- Normal results should be between 6.5 and 6.8. • Human urine - pH range is 6.0 - 6.5 in the morning and between 6.5 - 7.0 later in the day. • (Note: Bacteria usually increase the pH, as they break down urea in the urine into ammonia). • Human milk- pH range is between 7.0 to 7.4.

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