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Chemistry Clues

Ac i d s a n d B a s e sGenreExpository

Text FeaturesContents Chapter Headings Index SidebarsChapter Titles Glossary Experiments DiagramsPhotographs Illustrations Charts Captions

Organizational PatternsConcept/Definition Description

Vocabularyacid base compound corrosive indicator ion molecule neutral neutralization pH pigment reactivesalt scaling solution

OverviewA “tour” introduces many of the acids and bases found in most homes. Background information on

atoms and ions is provided for a better understanding of how acids and bases are defined. An ion is an atom with a positive or negative charge.

Acids are compounds that release hydrogen ions. They are proton donors. Acids taste sour, turn blue litmus paper red, conduct electricity in solution, form gases during certain reactions, and react with bases to form a salt and water. Hydrochloric, sulfuric, carbonic, ascorbic, and citric acids are common acids.

Bases are compounds that release hydroxide ions or accept hydrogen ions. They are proton acceptors. Bases taste bitter, feel slippery, turn red litmus paper blue, conduct electricity in solution, and react with acids to form a salt and water. Sodium bicarbonate, sodium hydroxide, and ammonia are common bases.

Indicators are materials that determine whether a substance is an acid, a base, or neither (neutral). Litmus paper, bromothymol blue, phenolphthalein, and many plant pigments are indicators.

The measure of the strength of an acid or base is called pH. The pH scale is a range of pH values from 0 to 14. Neutral substances are a 7. Substances with pH levels below 7 are acids. Substances with pH levels above 7 are bases.

Acids and bases are at work in the ground, in the air, and in the water. They perform important jobs in the human body. Many foods and products wouldn’t exist without acids and bases. Examples of these everyday acids and bases are featured.

For the Teacher

Editorial Director: Susan C. ThiesEditor: Mary L. BushDesign Director: Randy MesserBook Design: Emily J. Greazel Cover Design: Michael A. Aspengren

A special thanks to the following for his scientific review of the book: Kristin Mandsager, Instructor of Physics and Astronomy, North Iowa Area Community College

Image credits:©CDC/PHIL/CORBIS: p. 22; ©Stockfood America: p. 27 (bottom)

Brand X Pictures Royalty-Free: pp. 5 (bottom), 26, 28, 31; Rubberball Royalty-Free: p. 11 (top left); iStock International Inc. Royalty-Free—p. 24 (bottom); ©Jaimie D. Travis: p. 5 (top); ©Tom Longmate: p. 11 (top right); ©Rebecca Ellis: p. 13; ©Tom McNemar: p. 18 (bottom); ©Kenny Chi: p. 23; ©Jack Schiffer: p. 24 (top); ©Greg Nicholas: front cover (bottom center), p. 25 (top); ©Micheal Osterrieder: p. 25 (bottom); ©Ty Smith: p. 27 (top); Getty Images Royalty-Free: p. 6; Perfection Learning: back cover, front cover (bottom left and right), pp. 3, 7, 8, 9, 11 (bottom), 14, 17, 18 (top), 19, 21, 32; Photos.com: front cover (background), pp. 1, 4A special thanks to the following for her contribution of photoshoot supplies: Mrs. Deaver, Science Teacher, Ankeny High School

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1. A TOUR OF ACIDS AND BASES . . . . . . . . . . 4

2. BACKGROUND INFORMATION FOR

ACIDS AND BASES . . . . . . . . . . . . . . . . 7

3. ANSwERS ABOUT ACIDS . . . . . . . . . . . . . 9

4. BACK TO THE BASES . . . . . . . . . . . . . . . 13

5. ACID OR BASE? . . . . . . . . . . . . . . . . . 16

6. STRONG OR wEAK? . . . . . . . . . . . . . . . 19

7. ACIDS AND BASES AT wORK . . . . . . . . . . . 23

INTERNET CONNECTIONS AND RELATED READING FOR ACIDS AND BASES . . . . . . 29

GLOSSARy . . . . . . . . . . . . . . . . . . . . . 30

INDEX . . . . . . . . . . . . . . . . . . . . . . . 32

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The tour bus is now departing. Please climb aboard for a home tour. We will peek inside cabinets.

We will read labels. What are we looking for? We’re searching for acids and bases.

Acids and bases are very useful around the house. You’ll find them in baking products, medicines, cleaning agents, and more.

But be careful. These substances can be very dangerous. Strong acids and bases can burn your skin. Many of them are not edible and can make you sick. But if you’re willing to risk the danger, hop on the bus for an acid and base tour of your home.

First stop: the KitchenThe first stop is the kitchen. Open

some of the cabinets and you’ll find a variety of acids and bases. Baking powder and baking soda contain chemical bases. Vinegar is made from acetic acid. The loaf of whole grain wheat bread is a good source of folic acid.

Check the refrigerator. Vinegar-and- oil salad dressings are acidic. Soda tastes tart because it has carbonic acid. Lactic acid gives yogurt and buttermilk its sour taste. Reach in the back for that jar of pickles. The pickle juice contains acetic

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acid. Open up the fruit and vegetable drawer. Many fruits, such as apples and oranges, contain citric acid. Look at the labels of real fruit juices. You’ll notice that citric acid is a common ingredient. It gives the juices their tangy flavor.

Now search around and under the kitchen sink. Bases in dish soap and dishwasher detergent give them their cleaning power. Window and floor cleaners often contain bases. The oven cleaner you use to get the burned food off the bottom of your oven does too.

next stop: the BathroomClimb back on the bus. The next stop

is the bathroom. Look at all the tubes and bottles sitting around the sink and in the shower. Toothpaste, shampoo, and hand and body soaps all contain bases.

Open the cabinets under the sink. Toilet bowl cleaner contains a weak acid. The drain cleaner that breaks up all the hair that clogs your drains has a strong base.

The medicine cabinet is another storage area for acids and bases. Aspirin is an acid. Antacids are bases used to calm an upset stomach.

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Final stops: the laundry room and the GaraGeThe final stop on the tour is the garage. On the way to the garage,

we pass by the laundry room. The laundry detergent sitting next to the washing machine is a base. The spot removers in the cabinet may be too.

We reach the garage. A very strong acid is stored in the battery under the hood of the family car. Two bags of lawn fertilizers sit on a garage shelf. These strong bases help the grass grow thick and green.

the end oF the tour The tour bus is now unloading. Thank you for traveling with us and

being safe during the tour. Watch your step as you continue to learn more about acids and bases.

So what are all these acids and bases that you found on your tour? They both begin with atoms and ions.Atoms are the tiny pieces of matter that make up

all things. Normally atoms are neutral. This means that they have an equal number of positively charged protons and negatively charged electrons. The positive and negative charges balance one another, so the atom has a neutral charge.

When an atom gains or loses electrons, it becomes an ion. Ions are atoms with a positive or negative charge. An atom that gains electrons becomes a negatively charged ion. An atom that loses electrons becomes a positively charged ion.

When atoms combine with one another to form compounds, they exchange or share electrons. When they do this, the atoms become ions.

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Flourine atom (F)

Flouride ion (F-)

e

e

e

e

e

e

ee

e

e

e

e

e e

e

e

ee

e

protons (+9)

protons (+9)

electrons (-9)

electrons (-10)

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For example, when sodium and chlorine join together, the sodium atom gives one of its electrons to the chlorine atom. This makes the sodium and chlorine ions because now the sodium has one less electron than protons and the chlorine has one more electron than protons. The sodium now has a charge of +1, while the chlorine has a charge of –1.

Acids and bases are compounds that either gain or lose a specific type of ion when they react with other substances.

notes on Writing ionsEvery element can be abbreviated. Sodium, for example, is Na

and chlorine is Cl. when an element becomes an ion, a positive or negative charge is added to its abbreviation—for example, Na+ and Cl-.

If only one electron is gained or lost, just the – or + symbol is used. If more than one electron is gained or lost, then the number of electrons exchanged goes before the symbol. For example, when an atom of oxygen gains 2 electrons, it is written like this: O2 –.

Fluorine

Argon

Na+ Cl-

Na+

Cl-

An acid is a compound that releases hydrogen ions when dissolved in water. Hydrogen ions (H+) are hydrogen

atoms that have given away their only electron so they are no longer neutral. The hydrogen ion now has a positive charge. Acids are, therefore, also known as proton donors.

properties oF acidsAcids have certain chemical properties that classify

them as acids. Acids taste sour. In fact, the word acid comes from the Latin word acere, which means “sour.” If you’ve ever tasted lemon juice, vinegar, or aspirin (before you swallow it), you’ve experienced the sour taste of an acid. You should never, however, try to taste nonedible or unknown acids because they may burn or poison you before you have a chance to notice their sour taste.

Another property of acids is their effect on litmus paper. Litmus paper is paper that has been soaked in a blue pigment called litmus. Litmus turns red when it comes in contact with an acid, so acids turn blue litmus paper red.

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Acids have the ability to conduct electricity when in solution (dissolved in water). The ions that are released from the acid allow an electrical current to be passed along.

Acids react with certain materials to form a gas. Acids react with a charged group of atoms called carbonate ions. When they do, carbon dioxide (CO2) gas is produced. Geologists use this property of acids to test rocks to see if they contain carbonates. When a few drops of an acid are squeezed onto a rock such as limestone or marble, the resulting CO2 gas will bubble and fizz.

Inquire and Investigate: Acid ReactionsQuestion: Does an acid produce carbon dioxide gas when it reacts with a

carbonate?Answer the question: I think that an acid _________________ produce

carbon dioxide gas when it reacts with a carbonate.Form a hypothesis: An acid (does/does not) produce carbon dioxide gas

when it reacts with a carbonate.Test the hypothesis:

Materials• vinegar (acetic acid)• eyedropper• piece of chalk (calcium carbonate)ProcedureR Squeeze a few drops of vinegar onto the piece of chalk. Observe what

happens.Observations: Bubbling and fizzing occurs where the vinegar touches the chalk.

Conclusions: An acid produces carbon dioxide gas when it reacts with a carbonate. The fizzing and bubbling you see is the formation of CO2 gas when the acid (vinegar) and the carbonate (chalk) react. Sodium acetate and water are also formed from the reaction.

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When acids react with reactive metals, they produce hydrogen gas (H2). The reaction corrodes, or eats away, the metal. Acids in water that runs through metal pipes, for example, can corrode the pipes. This is why acids are considered corrosive.

Acids react with bases to form a salt and water. This process is called neutralization because the remaining saltwater solution is neutral (neither an acid nor a base). Acids and bases neutralize each other because the H+ ions from the acid combine with the OH- ions from the base to form H+OH- molecules, also known as H2O, or water. An example of this is the reaction between hydrochloric acid and the base sodium hydroxide. The result of the reaction is sodium chloride (table salt) and water. The reaction is written like this: HCl + NaOH → NaCl + H2O.

HydrochloricAcid

SodiumHydroxide

Water

Salt

Common Acids

Acid Name Chemical Formula

Strong or Weak? Facts

hydrochloric acid(also known as muriatic acid)

HCl strong

• breaks down food in the stomach

• used to clean metal and brick surfaces

sulfuric acid H2SO4 strong • found in car batteries

acetic acid (vinegar) HC2H3O2 weak

• found in salad dressings and other foods

• used for household cleaning

carbonic acid H2CO3 weak

• provides the sharp taste in pop and wine

• eats away at limestone, forming caves

citric acid H3C6H5O7 weak

• found in citrus fruits• used to give foods and sodas

a sour taste• used in soaps and detergents

to help them foam up in hard water

ascorbic acid (vitamin C) H2C6H6O6 weak

• found in fruits and vegetables• is very important to good

health; plays a role in many bodily functions

acetylsalicylic acid (aspirin) HC9H7O4 weak • used to reduce pain and

swelling

nitric acid HNO3 strong • used to make fertilizers, explosives, and nylon

folic acid C19H19N7O6 weak

• found in foods, particularly vegetables, fruits, nuts, and grains

• helps prevent brain and spinal defects in growing babies

• helps maintain good health in men and women

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A base is a compound that releases hydroxide ions (OH-) or accepts free hydrogen ions (H+) in solution. Bases

are proton acceptors.

properties oF BasesBases also have chemical properties that define them.

Bases taste bitter. Try tasting baking soda or baking powder and you’ll get the picture. Cough syrups also contain bases, which is why they need lots of flavoring to taste good. Like acids, many bases should never be tasted. If you drank ammonia or the lye used to make drain cleaners, the bitter taste would be the least of your problems!

a Base by another nameAlkali is another name for a base.

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Bases feel slippery or “soapy” to the touch. Detergents and soaps are bases, which is why they have that slippery feel. Bases dissolve grease and oil on your skin and react with other ingredients to clean your hands and your laundry.

Bases turn red litmus paper blue. Red litmus paper has already been exposed to an acid. When it comes in contact with a base, the paper turns blue again.

Bases share their last two properties with acids. A base can conduct electricity in solution just like an acid can. And, of course, if an acid reacts with a base to form a salt and water, then it can also be said that a base reacts with an acid to form a salt and water.

remembering the “Basics”having trouble remembering which color an acid or a base turns

litmus paper? Just remember that b stands for base and blue. a base turns litmus paper blue.

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Common Bases

Base Name Chemical Formula

Strong or Weak? Facts

sodium bicarbonate(baking soda) NaHCO3 weak

• used to make baked goods rise

• found in toothpastes to help remove stains from teeth

• absorbs odors• main ingredient in

some antacids

magnesium hydroxide Mg(OH)2 weak• main ingredient in

milk of magnesia, an antacid and laxative

sodium hydroxide(lye) NaOH strong

• found in powerful drain cleaners

• an ingredient in soaps and detergents

• used to make paper

calcium hydroxideand calcium oxide(lime)

Ca(OH)2CaO strong

• found in mortar and plaster used for construction

• used to neutralize acidic soil

• used in water and sewage treatment to reduce acidity

ammonia NH4 weak • used as a household cleaner

Tracing the Path of ScienceRobert Boyle, an English chemist in the 1600s, was the first

person to classify substances as either acids or alkalis (bases). He listed their opposite chemical properties and noticed their ability to counteract each other.

But it wasn’t until the late 1800s that Svante Arrhenius, a Swedish scientist, proposed a reason why acids and bases had such opposite characteristics. Arrhenius hypothesized that acids dissolve in water and release hydrogen ions. He also defined a base as a substance that dissolves in water and releases hydroxide ions. Unfortunately, this didn’t work in every case since not every base releases hydroxide ions and not all reactions of acids and bases involve water.

In 1923, Danish scientist Johannes Bronsted and Englishman Thomas Lowry made some insightful changes to Arrhenius’s proposals. The Bronsted-Lowry idea expanded the definition of bases to include any substance that accepts hydrogen ions. In other words, bases are proton acceptors and acids are proton donors.

Later in 1923, Gilbert Lewis, an American chemist, created a more general definition in which an acid is any compound that can accept a pair of electrons, while a base is any compound that can donate a pair of electrons.

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Understanding acids and bases did not happen overnight. It took hundreds of years for scientists to

piece together what is now known about these substances.

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Even after acids and bases were classified, it was often difficult to determine if a substance was an acid or a base. Many of the properties of acids and bases are hard to detect just by looking at or touching a material. So how do you tell if something is an acid or a base—or neither? You use an indicator. Indicators are materials that change color to show whether a compound is an acid, a base, or a neutral substance.

Litmus paper is a common indicator. Blue litmus paper turns red when dipped in acids. Red litmus paper turns blue when exposed to a base.

Bromothymol blue is a liquid indicator that changes from blue in bases to yellow in acids. To see bromothymol blue in action, put some water in a clear glass or test tube. Ask an adult to add some bromothymol blue. Gently blow through a straw into the solution. What happens? The color of the water will change to yellow. Why? The carbon dioxide in your breath reacts with the water to form carbonic acid. The bromothymol detects the acid and turns yellow.

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Phenolphthalein (fee nuhl THAY leen) is another indicator. This liquid is colorless in acids but turns bright pink when mixed with a base. When placed in a neutral solution, phenolphthalein changes to a very faint pink color.

You can make your own indicators using materials from a grocery store or garden. Many plants and flowers have pigments in them that act as indicators. These natural chemicals will change color when combined with an acid or base. Red (or purple) cabbage is one example. The cabbage juice mixed with water turns red to purple with acids, yellowish green with bases, and bluish purple with neutral materials.

Why is it that some acids and bases are strong enough to corrode metal while others are weak enough to

consume in foods and medicines? The answer lies in the strength of the acid or base.

Some acids and bases release or accept ions freely. Others don’t separate as easily. More of their molecules stay together, even in solution.

In strong acids, most or all of the hydrogen ions break free and “float” around in the solution. The more free hydrogen ions, the stronger the acid. In a weak acid, only a small portion of the molecules form ions when in solution.

Strong bases take up almost all of the hydrogen ions in a solution or have molecules that let go of hydroxide ions easily. A weak base accepts only a small portion of hydrogen ions or splits up only some of its molecules into ions.

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H+

H+H+

H+H+

H+

H+ H+

H+

H+

H+H+

H+

Strong acid Weak acid

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phThe measure of the strength of an acid or base is called pH.

Substances with low pH are acids. Substances with high pH are bases.

Scientist of SignificanceSoren Sorensen was a Danish biochemist who developed the idea of pH.

Sorensen was a chemistry student and later a professor at the University of Copenhagen. In 1901, he became the head of the Chemical Department at Carlsberg Laboratory. The laboratory specialized in researching the chemistry of the human body.

while at Carlsberg, Sorensen performed numerous studies on how acids and bases affected the body. His work led him to suggest that the concentration of hydrogen ions found in a substance should be measured in a standard way. He established the pH scale in 1909, and it was used immediately at the laboratory. Gradually the scale was accepted by other chemists. By the 1930s, the use of Sorensen’s pH scale was worldwide.

The pH scale is a range of pH values from 0 to 14. All compounds fall somewhere on the scale.

Neutral substances are a 7 on the pH scale. The farther a pH number is from neutral (7), the stronger the acid or base is. Numbers below 7 on the pH scale are acids. A 6 is a weak acid, while a 0 is an extremely strong acid. Numbers above 7 on the scale are bases. An 8 is a weak base, while a 14 is a very strong one.

Each number on the pH scale is actually 10 times stronger or weaker than the number next to it. For example, when comparing two acids whose pH levels are 2 and 4, those acids are two spots away from each other on the scale. The acid with the pH of 2 is therefore 102 times (or 100 times) stronger than the acid with the pH of 4. So lemon juice is 100 times more acidic than a can of soda.

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The pH Scale

pH Example

Acid

0 strong hydrochloric (stomach) acid

1 sulfuric (battery) acid

2 lemon juice

3 vinegar

4 soda

5 rainwater

6 weak milk

Neutral 7 pure (distilled) water

Base

8 weak egg whites

9 baking soda

10 antacids

11 ammonia

12 calcium hydroxide (lime)

13sodium hydroxide (lye)

14 strong

VinegarLemon juice

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Technology LinkThere are several tools used to measure the pH of substances. The simplest

is pH paper. This is a special paper that changes color depending on the concentration of an acid or base. while pH paper gives a general idea of how strong an acid or base is, it does not provide an exact pH measurement.

The first electronic devices used to determine exact pH levels were invented in the 1920s. These machines became known as pH meters. A pH meter has a glass bulb on one end and an electrical wire on the other. when the bulb is dipped into a solution, the meter can sense differences in the electrical charges inside and outside the probe. This determines the concentration of hydrogen ions in the solution.

Today, pH pens make measuring pH even more convenient. These “pens” are small, compact meters that resemble digital thermometers. They are lightweight and easy to carry.

Acids and bases are at work in the ground, in the air, and in water. They perform important jobs in your

body. Many of the foods and other products you rely on every day wouldn’t exist without acids and bases.

With WaterWater is constantly interacting with acids and bases.

When carbon dioxide reacts with water in the air, it forms carbonic acid. This makes rainwater a weak acid. Normal rainwater has a pH level of about 5.5. The acid in rain eats away at rocks containing lime. Statues and buildings above ground are gradually worn down. When rainwater trickles underground, it carves through limestone, creating caves.

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When rain becomes too acidic, it’s called acid rain. Acid rain has a pH below 4.5. Human activities, such as power production, manufacturing, and driving, increase air pollution. Sulfur dioxide (SO2) and nitrogen oxide (NO) are common pollutants. When these chemicals react with water in the atmosphere, they create sulfuric acid (H2SO4) and nitric acid (HNO3). These strong acids can kill plants, fish, and other living things in lakes and ponds. They can also speed up the erosion of statues and buildings made of rock such as limestone and marble.

When normal rainwater or acid rain is absorbed into the soil, it makes the soil more acidic. Too much acidity is bad for plant growth. Farmers or gardeners with too much acid in their soil can add lime (a base) to help return it to healthy pH levels.

Fish tanks and swimming pools also have pH issues. Fish need a pH level of 5.5 to 8.4 to be healthy. Test kits can help fish owners determine the pH of their tanks. If the water is too acidic or basic, then acids or bases can be added to the water to adjust the pH level.

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If you spend a lot of your summer swimming in the city pool, you might be concerned with the water’s pH. The water in a pool should have a pH of 7.2 to 7.6. This level doesn’t cause skin irritation, prevents corrosion or scaling of the pool, and kills harmful organisms at a safe rate. A base such as sodium carbonate or an acid such as muriatic acid can raise or lower the pH of pool water.

in the BodySeveral acids play important roles in your body. Every cell in your

body contains deoxyribonucleic acid (DNA). This is the genetic material that controls all of the chemical reactions in your body. Amino acids are the building blocks of proteins. Each of the million different proteins in your body has a job such as growing new cells or building muscles. Ascorbic acid helps keep your bones, skin, and teeth healthy.

DNA simulation

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Your digestive system makes use of both acids and bases. The hydrochloric acid in your stomach helps break down the food you eat into simpler products that your body can use. As the food moves into the intestines, the pH level rises to slightly basic levels. This allows “good” bacteria to process and absorb nutrients from the food.

Too much of some acids can cause problems in the body. When lactic acid builds up in muscles, it can cause aching and cramping. Oxygen changes the lactic acid to other materials that don’t harm the muscle. This is why sometimes you need to stop and take deep breaths when you’re running.

Excess acid in body organs can have serious consequences. When a body has too much acid, it tries to get rid of it. This takes important minerals away from their “regular” jobs such as preventing illnesses or digesting food efficiently. One easy thing you can do to prevent acid overload in your body is to eat more “basic” foods, such as the majority of fruits and vegetables.

ph-Balanced BloodHealthy blood in the human body has a pH of 7.4.

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in FoodsAcids and bases are found in many foods you enjoy. Citric acid is just

one of many acids found in a variety of fresh and processed food. Lemons, limes, and other “sour” fruits are great sources of citric acid. Cheeses, jams, desserts, and other sharp or fruity-flavored foods also contain citric acid. Juices and sodas get their tart taste from this acid as well.

Bases are essential for baking. A reaction between baking soda or baking powder and other ingredients in cakes, cookies, or breads produces carbon dioxide gas. This gas makes the product rise and causes it to be light and airy. Baking soda is usually used when there is already an acidic ingredient in the recipe (fruit juice, vinegar, buttermilk, sour cream) to counteract the bitter flavor of the base. Baking powder is just

baking soda with an acidic compound (such as cream of tartar) and cornstarch already mixed in. The added acid helps neutralize the base. The cornstarch keeps the mixture smooth and prevents clumping.

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in productsAcids and bases are found in many useful products.

Acids are found in fertilizers, plastics, petroleum products, and batteries. Bases are found in fertilizers, construction materials, paper, and soaps. Both acids and bases are found in a variety of cleaning products.

Acids and bases can make you feel better. Acetylsalicylic acid is better known as aspirin. Cough syrups often contain bases. Antacids such as Tums, Rolaids, Milk of Magnesia, and Pepto-Bismol are bases that counteract excess stomach acid.

_________________

Acids and bases are at work all around (and inside) you. If you continued your acid and base tour around your school or community, you’d be amazed at all the places you’d find these important substances. You really do depend on them every day!

ph-Balanced productsmany products you use on your skin and hair may keep you

clean and make you smell good, but excessive hygiene is not as healthy as you might think. oils and other chemicals on your skin normally protect it from infection. soaps and shampoos contain a base called lye. Bases dissolve oils and greases on the skin, which is why they clean well. however, they also remove the good oils that your skin needs. dry skin can itch or hurt. it can also crack and increase the risk of germs entering the body.

to solve this problem, many shampoos and soaps are “ph balanced.” this means that they have added chemicals to bring their ph level closer to skin’s natural ph of 5.

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http://www.chem4kids.com/files/react_acidbase.htmlChem4Kids introduces you to acids and bases.

http://www.chemtutor.com/acid.htmThis online tutoring site gives you the basics on acids and bases.

http://www.visionlearning.com/library/module_viewer.php?mid=58Get a clearer vision of acids and bases with this information.

http://www.miamisci.org/ph/Explore the “pH Factor” with the facts, charts, and activities at this hands-on site.

http://www.ec.gc.ca/acidrain/kids.htmlFind out more about pH and acid rain with these questions and answers, graphics, and experiments.

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Acids and Bases by J. M. Patten. A book about acids and bases, what they do, and how they are useful in everyday life. Rourke Book Company, Inc., 1995. ISBN 1-5591-6128-0. [RL 5 IL 2–6] (0216706 HB)

•RL = Reading Level•IL = Interest LevelPerfection Learning’s catalog numbers are included for your ordering convenience. HB indicates hardback.

acid (AS id) substance that releases hydrogen ions (see separate entry for ion)

base (bays) substance that accepts hydrogen ions or releases hydroxide ions (see separate entry for ion)

compound (KAHM pownd) substance made up of more than one type of element or atom

corrosive (kuh ROH siv) able to wear away something by chemical action

indicator (IN duh kay ter) substance that changes color to indicate whether a substance is an acid, a base, or neither

ion (EYE on) atom that is positively or negatively charged because it has lost or gained electrons

molecule (MAHL uh kyoul) one or more atoms held together by chemical forces

neutral (NOO truhl) neither an acid nor a base

neutralization (noo truh luh ZAY shuhn) reaction between an acid and a base that results in a salt and water (see separate entry for salt)

pH (pee aych) measure of the strength of an acid or base

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pigment (PIG ment) natural substance in a plant or animal that gives it its color

reactive (ree AK tiv) referring to elements that react quickly and easily with other elements

salt (sawlt) compound formed as a result of the reaction between an acid and a base (see separate entry for compound)

scaling (SKAY ling) coming off in pieces or flakes (scales)

solution (suh LOO shuhn) mixture in which one or more substances are dissolved evenly in another substance

acid and base indicators, 17–18acids definition, 9, 16 examples, 4, 5, 6, 12,

23–24, 25, 26, 27, 28 properties, 9–11Arrhenius, Svante, 16bases definition, 13, 16 examples, 4, 5, 6, 15, 26,

27, 28 properties, 13–14Boyle, Robert, 16Bronsted, Johannes, 16ions, 7–8

Lewis, Gilbert, 16Lowry, Thomas, 16neutralization, 11, 14pH, 19–22, 24–25, 28pH indicators, 22pH scale, 20, 21–22Sorensen, Soren, 20

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pH meter

Earth and Space StrandsAmazing SpaceDown to Earth!

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How Things Are MadeThe Material World

Science Works!

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Communities of LifeHabitats

Healthy LivingThe Human Body

Human Body BasicsLife Science Investigations

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