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

Images shutterstock.com

Ions:Charged Particles

in Solution

Chapter 6Remind Ms J to clock in On Oct 6th we’ll go to the

Webb at 3:20pm

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.

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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Ionization

©Goodheart-Willcox Publisher

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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-)



Hydrogen, hydronium, and hydroxide ions are used to define acids and basesAcids 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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Salt:when acids and bases form a compound with ionic bondsNeutral substances like pure water have a balance of positive and negative charges

Water always has an equal number of hydronium and hydroxide ions

©Croisy/Shutterstock.com


Bronsted-Lowry Theory

• Johannes Bronsted and Thomas Lowry found that acids and bases separate in water to form ionsAcids are: proton donorsbases are:proton acceptors

Acids and bases naturally react with their opposites to achieve a neutral chargecontinued


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


Identifying Acids and BasesSensory evaluation of safe substances can identify acids and bases through

Touch: Bases have a slippery feelTaste: Acids are sour and bases are bitter ©marylooo/Shutterstock.com

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Identifying Acids and BasesOrganic 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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Identifying Acids and BasesAcids 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

©Peter Zijlstra/Shutterstock.com


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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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


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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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


Measuring Concentrations of Acids and Bases• Avogadro’s number of particles of

any substance is known as a moleOne 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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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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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


pH and Baking

• pH affects flavor, color, and textureA chemical leavening agent is an acid and a base that neutralize batters and doughs to lighten or aerate baked products

continued©Eldred Lim/Shutterstock.com


Chemical leavening agents include:

What does baking soda do?It’s a base that needs an acidic ingredient to produce carbon dioxide for leaveningWhat does baking powder do?Includes baking soda, dry acids, and a filler that leavens when liquid is added and again when the mixture is heatedWhat does ammonium bicarbonate do?Produces ammonia gas so is only used commercially

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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


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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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

Documents

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