May 21, 2012AGENDA:1 – Bell Ringer &

Part. Log2 – CN: Acids &

Bases3 – pH Practice

Questions4 – Summary &

Questions

Today’s Goal:Students will be able to compare and contrast acids and bases.Homework1. Complete summary and

questions based on notes.

2. Week 35 work is due by Friday.

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

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.

Fruits such as citruses, cranberries and tomatoes are acidic.

Acids also help you to digest foods Gastric Acid (Hydrochloric Acid

and other digestive enzymes).

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).

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?

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).

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.

Auto-ionization of Water *

Pure water produces an equal number of hydrogen ions (H+) and hydroxide ions (OH-):

H2O (l) H+ ion (aq) + OH- ion (aq)

2H2O (l) H3O+ ion (aq) + OH- ion (aq)

(hydronium ion)

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 Acids

Citric 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 Bases

Detergents, Soap,Lye (NaOH),

Household Ammonia

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.

Acid / Base Strength: The pH Scale *

Using the diagram, answer the following:

The lower the pH the more “__________”.

The higher the pH the more “__________”.

PRACTICE PROBLEMS: Label each of the following as either: ACIDIC, BASIC, OR NEUTRAL.

1. 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).

2. Human saliva - Normal results should be between 6.5 and 6.8.

3. 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).4. Human milk - pH range is between 7.0 to

7.4.

What you know about your body:

Which is Acidic and Basic?