1. Ions: Charged Particles in Solution
On Oct 6th we’ll go to the Webb at 3:20pm
Remind Ms J to clock in
Chapter 6
Ions: Charged Particles in Solution

2. Defining Acids and Bases
Acids, bases and salts are factors in food preservation and wine, cheese, and bread making
They play a key role in digestion and other bodily functions
Ionic bonds are the basis for learning about acids and bases and how they react in foods
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3. Ionization is the process of forming ions
During the ionization of water:
A hydrogen atom breaks away and becomes a positively charged hydrogen ion that bonds with a water molecule, forming a hydronium ion (H3O+)
The hydrogen atom remaining in the OH group shares its electron with the oxygen atom, forming a negatively charged hydroxide ion (OH-)
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4. Defining Acids and Bases
Hydrogen, hydronium, and hydroxide ions are used to define acids and bases Acids produce: hydrogen or hydronium ions in water-based solutions and have a positive charge Bases produce: hydroxide ions in water-based solutions and have a negative charge
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5. Defining Acids and Bases
Salt: when acids and bases form a compound with ionic bonds Neutral substances like pure water have a balance of positive and negative charges
Water always has an equal number of hydronium and hydroxide ions
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6. Bronsted-Lowry Theory
Johannes Bronsted and Thomas Lowry found that acids and bases separate in water to form ions
Acids are:
proton donors
bases are:
proton acceptors
Acids and bases naturally react with their opposites to achieve a neutral charge
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7. Lewis Theory
Gilbert Newton Lewis discovered acid/base reactions could be described in terms of movement of electrons
If hydrogen is not involved, bases donate electrons and acids accept electrons
This helps explain how carbon dioxide is an electron acceptor and causes the acid/base reaction in soft drinks

8. Identifying Acids and Bases
Sensory evaluation of safe substances can identify acids and bases through
Touch: Bases have a slippery feel
Taste: Acids are sour and bases are bitter
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9. Identifying Acids and Bases
Organic dyes are color pigments that change color with acids or bases
litmus paper: Bases turn it blue; acids, red
pHydrion paper: Bases turn it yellow green to blue green; acids turn it yellow to orange red
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10. Identifying Acids and Bases
Acids and bases affect fruits and vegetables that contain organic dyes
Green vegetables turn brighter if a base is added when cooking
Red cabbage turns bluish purple in alkaline liquid
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11. Measuring Acids and Bases
Acids and bases can be “weak” to “strong”
Scientists use accuracy when measuring acidity and alkalinity
A pH scale expresses the degree of concentration of hydrogen or hydronium ions present in a solution
The more hydronium ions in a solution, the more concentrated the acid will be
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12. Measuring Acids and Bases
Each number in the pH scale represents 10 times greater or fewer hydronium ions
Acids : 1.0 to 6.9
7.0 is considered neutral
Bases :7.1 to 14.0

13. Measuring pH
Organic dyes, or indicators, demonstrate the degree of acidity of a solution through color change
A pH meter is needed to ensure accuracy
Titration:
is the method of adding an acid with a known pH to an unknown base or adding a base with a known pH to an unknown acid
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14. Measuring pH
burettes dispense the known acid or base one drop at a time until the endpoint, or equivalence point (neutralization occurs)
color changes, scientists calculate how many acid molecules it took to neutralize base molecules
Neutralization: acid molecules = base molecules
Titration requires knowing the volume and concentration of a solution

15. Measuring Concentrations of Acids and Bases
Avogadro’s number of particles of any substance is known as a mole
One mole of an element = mass in grams listed on the periodic table
Solute concentrations must be measured in terms of molarity (M)
Molarity = moles of a solute per liter of solution
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16. pH and Digestion
pH balance of enzymes and stomach acid is critical to the digestive process
Buffer: compound that helps stabilize pH by absorbing excess acids or bases in a solution
We coat some aspirin tablets to aid with digestion and prevent damage to the digestive system
Buffering salts or proteins as added to processed foods to stabilizing their pH
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17. pH and Food Preservation
Knowing the pH environment in which bacteria grow best is crucial to preserving food and keeping it safe
Botulism is caused by a toxin that affects low-acid foods with a pH above 4.6
Yeasts grow in a pH range from 4.0 to 7.0
Molds grow in a pH range from 2.0 to 8.5
Salts work to preserve food by dehydration

18. pH and Baking pH affects flavor, color, and texture
A chemical leavening agent is an acid and a base that neutralize batters and doughs to lighten or aerate baked products
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19. Chemical leavening agents include:
What does baking soda do? It’s a base that needs an acidic ingredient to produce carbon dioxide for leavening What does baking powder do? Includes baking soda, dry acids, and a filler that leavens when liquid is added and again when the mixture is heated What does ammonium bicarbonate do? Produces ammonia gas so is only used commercially
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20. pH and Baking
The pH changes in batters and doughs affect color and texture of baked products
Acids such as lemon juice or cream of tartar are added to angel food cake to develop the white color
Chocolate cakes have a deeper, darker color and smoother flavor if the batter is more basic

21. pH and Eggs
Eggs become more basic in storage as CO2 escapes through the egg shell
Mousse, soufflés and meringues need fresh eggs because their thicker egg whites trap more air
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22. pH and Fruit Maturity
As fruits mature, acids develop that improve juice quality, affect color, and increase sugar content
Testing pH levels of fruit helps determine the ideal harvest time
Food scientists created charts for citrus growers showing the best harvest time for peak flavor