Science Lab in the Supermarket (Illustrated)
Page 1
Science Lab
in a
Supermarket
by
BOB FRIEDHOFFER
Illustrated by
Joe Hosking
FRANKLIN WATTS
A Division of Grolier Publishing
New York London Hong Kong Sydney
Danbury, Connecticut
To Martin Gardner, who has
made the study of science and math
a supermarket full of surprises and joy.
Note to Readers: Words that appear in italics are defined in a glossary at the back of the book.
Visit Franklin Watts on the Internet at: http://publishing.grolier.com
Library of Congress Cataloging-in-Publication Data
Friedhoffer, Robert. Science lab in a supermarket / by Bob Friedhoffer; illustrated by Joe Hosking.
p. cm. — (Physical science labs)
Includes bibliographical references
Summary: Presents a variety of experiments using items you can buy in the supermarket. Also explains the scientific basis for such things as the flexible plastic strips that cover doorways leading into the meat departments in many large markets.
ISBN 0-531-1 1335-3 (lib.bdg) 0-531-15844-6 (pbk)
1. Science—Experiments—Juvenile literature. 2. Physics—Experiments—Juvenile literature. 3. Supermarkets—Study and teaching—Activity program—Juvenile literature. [I. Science-Experiments. 2. Experiments. 3. Supermarkets.] I. Hosking, Joe, ill.
II. Title. III. Series.
Q164.F693 1997
540'.78-dc21 96-37285 CIP AC ©1998 by Bob Friedhoffer
All rights reserved. Published simultaneously in Canada.
Printed in the United States of America
1 2 3 4 5 6 7 8 9 10 R 07 06 05 04 03 02 01 00 99 98
Acknowledgments
To my friends and family who shop in supermarkets:
Rodney "Butler of the Woods" Ezrapour, who sweeps up and down the aisles of the supermarket
Vinny "31908" Manta, who polices the pasta aisle
Les "Mr. Lucky" Spiewak, who doggedly pursues the ultimate diet
Stanley "Club Mud" Spiewak, who always brings home the bacon
Peter and Jackie Monticup, who single-handedly support the pet-food aisle
Harold Underdown, who supports the stationery aisle with his purchases of Wite out®
Nikki, who shops the designer produce section only
Annette, who sends me out to buy the groceries
CONTENTS
INTRODUCTION
CHAPTER ONE - IS WHAT YOU SEE WHAT YOU GET?
Why Is Food Packaged?
A Big Trick: The Size of Detergent Containers
Fooling the Senses
CHAPTER TWO - PRODUCE SECTION
Fruits and Vegetables
How Water Travels Through Plants
Crying in the Kitchen
Popcorn! Get Your Fresh Popcorn Here!
CHAPTER THREE - SUPERMARKET STAPLES
Going, Going, Gone
It's a Delicate Balance
A Closer Look at Density
Not a Drop to Drink
Rock Candy
CHAPTER FOUR - PASTA, MACARONI, SPAGHETTI, AND OTHER NOODLES
CHAPTER FIVE - THE SODA AISLE
It's All About Pressure
Diet vs. Regular: Which Weighs More?
CHAPTER SIX - CLEANING SUPPLIES
Soap: A Brief History
How Soap Cleans
Pure or Pure Malarkey?
Detergents
The Laundry Blues
Cleaning with Scratchy Stuff
The Mohs' Scale: What Does Harder Mean?
CHAPTER SEVEN - GETTING STUFF OUT OF BOTTLES
Aerosol Spray Cans and Bottles
Spray Cans
Spray Bottles
Baby Bottles
CHAPTER EIGHT - THE COOLER AND FREEZER AISLES
Some Cool Questions (and Answers)
CHAPTER NINE - THE DAIRY CASE
Where Does Cream Come From?
How to Whip Cream
Before It's Butter
I Scream, You Scream, We All Scream for Ice Cream
APPENDIX
GLOSSARY
RESOURCES
Books
Internet Sites
Science Lab
Supermarket
Introduction
You probably don't think of a supermarket as a science laboratory. After all, you go to a supermarket to buy food, cleaning supplies, or paper products—not to conduct experiments. The truth is every aisle, shelf, nook, and cranny of a supermarket could be the source of a scientific wonder. All you have to do is take the time to look around and use your imagination. Items found in the produce aisle can teach you about biology. The aisle with cleaning products offers all kinds of lessons in chemistry. The dairy aisle can teach you something about science too. Wherever you look, you can study the sciences.
The order and location of the aisles and the arrangement of the shelves have all been carefully designed to get customers to buy as much as possible. The strategies used by supermarket designers are based on the science of psychology, which looks at the behavior of human beings.
Scattered throughout this book you will find a safety symbol. Ask an adult to help you whenever you see this symbol. The symbol indicates that an experiment is a little bit dangerous or difficult. I'd hate to see you get discouraged or hurt while you are learning about science in a supermarket.
Chapter One
Is What You See What You Get?
The packaging, displays, and labels you see as you bop around a supermarket might seem to have nothing to do with science. But if you pay attention, you can see potential scientific experiments— and the results of such experiments—all around you.
Just think for a moment. When you go into a supermarket, what do you see? Most food comes in boxes, cans, bags, or shrink-wrapped trays so the first thing you see is the packaging.
WHY IS FOOD PACKAGED?
Improvements in packaging are one reason that less food spoils in a modern supermarket than in the markets of 100 years ago—even though modern markets have larger quantities of food as well as a much greater variety At one time, dry food was kept in loose burlap sacks that were difficult to stack and display. Shopkeepers would measure out the exact quantity of each item a customer wanted. He would sell you 2 pounds of flour, ½ pound of sugar, 1 pound of green beans, and ¼ pound of coffee beans. The storekeeper had to measure and then pack each item.
Modern supermarkets have food in convenient, stackable cartons, boxes, jars, and bottles. Most food is packaged in containers that are just the right size for feeding a certain number of people. In many cases, packages of food are designed to feed a family of four people. In recent years, manufacturers have begun to package some foods in quantities that are appropriate for single people.
At one time, most dry foods were measured into paper bags, and liquids were usually poured into containers the customer brought from home. This way of selling goods meant that it took much longer to serve each customer. The prepackaged foods sold today save time. Because fewer workers are needed, it also means that each item can be sold at a lower price.
Food is also wrapped so that bacteria, dust, dirt, and water cannot contaminate it. Potato chips, pretzels, crackers, popcorn, bread, rolls, and cupcakes can absorb moisture from the air or lose moisture to the air. When these items become soggy or dry out, they are not very appetizing. That is why they are wrapped in airtight and moisture proof packaging that prevents humid air from coming in contact with the foods. As a result, they stay fresh and crisp.
Materials
Four small bags of potato chips
A clothespin
A Refrigerator
Procedure
1. On a hot, humid summer day, place one unopened bag of potato chips on the kitchen counter.
2. Open the other three bags of chips.
3. Leave one open bag on the kitchen counter.
4. Fold the top of another bag two or three times and prevent the bag from unfolding with the clothespin. Leave this bag on the counter, too.
5. Place the third open bag in the refrigerator.
6. After a day or two, compare the taste and texture of the potato chips in each of the four bags.
Which chips taste the best?
Results
The potato chips in the unopened bag should be fresh and crisp. The chips in the bag that was left open on the kitchen counter should be stale and soggy. The chips in the bag held shut with a clothespin should be as fresh as those in the unopened bag. The chips in the refrigerated bag should be crisper than those in the bag that you left open on the counter.
Why these different results? Salt is hygroscopic—it absorbs moisture easily. Foods with large quantities of salt get stale and soggy when left out in the air. Foods with large quantities of sugar react the same way to humid air.
On humid days, the air is full of moisture. Some of this moisture was absorbed by the chips in the open bag on the counter. The bag held shut with a clothespin was exposed to the humid air for only a few minutes, so it did not absorb much moisture. The humidity inside a refrigerator, especially a frost-free refrigerator, is usually quite low, so these chips should be almost as crisp as the chips in the unopened bag.
A BIG TRICK: THE SIZE OF DETERGENT CONTAINERS
At one time, Americans were less environmentally conscious than they are today. They were not too concerned about recycling or about buying products with large, wasteful packaging. They thought the bigger an item, the better it must be.
In an attempt to outdo each other, the companies that sell laundry detergent added fillers to their products. These fillers did nothing to help clean clothing. They just made the detergent look as though it was a better buy because it was in a box larger than their competitors' boxes, yet cost about the same amount of money. The manufacturers were tricking people.
In the last few years, detergent manufacturers have been reducing the size of their packaging. In response to the American interest in reducing waste, the detergent companies have removed some of the useless fillers from their products. Less filler means more cleaning power in a smaller box. Of course, these companies do not admit that they were ever adding useless fillers to their products. Their new advertisements claim that the detergents have been reformulated to make them much more powerful.
FOOLING THE SENSES
Some supermarkets and food packagers use a few tricks to make the food they sell look more appealing. For example, the fluorescent lighting fixtures in the meat cases of many supermarkets have pink or red filters. The red light gives the meat, especially beef, a deeper, richer color. Some butchers create the same effect by wrapping meat in plastic that is slightly pink or red. Is this cheating or just smart marketing?
Many supermarkets package meats in Styrofoam™ trays covered with plastic wrap. This packaging prevents dirt and germs from contaminating the meat, but it also prevents the customer from examining both sides of the meat. The side that is not visible might be very fatty or slightly discolored. There is no way for the customer to know exactly what he or she is buying.
Not long ago, some parts of the United States had a law requiring markets to package meats in clear plastic trays so that customers could see both sides of the meat. Unfortunately, some of these laws have recently been changed, so supermarkets can start using Styrofoam trays again. The store owners said they would save a lot of money by using the less expensive Styrofoam trays. They claimed they just wanted to pass these savings along to their customers and wouldn't dream of trying to outwit the consumer. What do you think?
Many supermarkets bake fresh breads and cakes right in the store. They do this to provide customers with fresh goods, but the owners also know that the smell of fresh-baked goods makes people happier and more likely to shop at their store. Some stores even install fans in the bakery and blow the wonderful smell of fresh-baked products throughout the store.
Have you ever noticed carrots packed in bags that have orange lines printed on the plastic? Many unsuspecting consumers decide to buy the carrots because it seems that the carrots inside are bright orange and tasty-looking. When they open the bag, however, they may find that the carrots are not quite as appetizing as they seemed in the store. The companies that distribute the carrots know that the orange stripes on the package make the carrots look more tempting.
Supermarkets sometimes put green filters on the lights in vegetable bins in the produce section. This makes the vegetables look greener and fresher.
Chapter Two
The Produce Section
FRUITS AND VEGETABLES
Every supermarket has a produce section. It is full of all kinds of fresh fruits and vegetables. Some—like apples and bananas are delicious; others—like brussels sprouts are yucky!
You know that bananas, apples, oranges, and peaches are fruits. Spinach, lettuce, and carrots are vegetables. But what is a tomato? How about a cucumber? You may think they are vegetables, but they aren't. They're both fruits. How can you tell the difference between a fruit and a vegetable?
According to botanists—scientists who study plants—a fruit is the portion of a plant that has seeds inside. Every other part of the plant the roots, the leaves, the seeds, and the stems—is a vegetable. We eat the roots of potato and carrot plants, the leaves of lettuce and spinach, the seeds of corn and peas, and the stems of celery and rhubarb.
So why do most people think that tomatoes and cucumbers are vegetables? The term "vegetable" is commonly used to describe plants that we normally eat as part of a salad or along with the main course. Examples include string beans, tomatoes, squash, and eggplant. All these foods contain seeds, but we call them vegetables anyway. Vegetables that don't have seeds—those a botanist would agree to call a vegetable include carrots, beets, spinach, onions, garlic, scallions, cabbage, and lettuce.
The items we call "fruits" are sweet foods. We usually eat apples, pears, oranges, grapefruit, pineapples, strawberries, and other fruits as dessert or snacks.
HOW WATER TRAVELS THROUGH PLANTS
Plants rely on a force known as cohesion to move water through tubes that run from their roots through their stems to their leaves. Cohesion is a force that causes water molecules to move toward each other. As water molecules in the leaves of the plant evaporate, the water below is pulled upward. In this way, the water lost to evaporation is replaced by water molecules from the stem. At the same time, water molecules from the roots replace the water molecules that have moved from the stem to the leaves. Cohesion makes this process possible.
OBSERVATION 1
Fill a bowl three-quarters full of water. Place one end of a 1-inch (2.5-cm)—wide strip of paper towel in the bowl of water. Hang the rest of the paper towel over the edge of the bowl. Check the strip every 15 minutes. You should see the water traveling along the length of paper towel.
Tear apart the paper towel and look at the edge with a strong magnifying glass. You should be able to see a network of tiny fibers. Each of these fibers is actually one of the tubes, or capillaries, that transported water through the plant that the paper towel was made from. Have you eaten fresh celery? If so, you probably noticed that it was stringy. Maybe the strings even got stuck between your teeth. Those "strings" are actually the capillaries that carry water from the roots of the plant to the leaves. In the next three experiments, you will use celery to learn more about how cohesion moves water through the capillaries of a celery plant.
EXPERIMENT 2
Materials
&n
bsp; A glass of water
Red food coloring (or red fountain-pen ink)
A bunch of fresh celery
A sharp knife
Procedure
1. Add red coloring to the water until it has a rich, deep color.
CAUTION: Food coloring or ink can stain clothing.
2. Tear a stalk of celery from the bunch. Ask an adult to cut the bottom of the stalk horizontally to form a straight edge. It will be necessary to use a sharp knife.
3. Place the stalk in the glass of colored water. The whitish base of the stalk should be immersed in the colored water; the top end should stick out of the glass.
4. Move the glass to a place where it will not be disturbed.
5. Examine the celery stalk every few hours. What do you see?
6. After 3 or 4 hours, ask an adult to slice the celery so that you can see a cross-section of it. What are those little dots of color on the cut portion?
Results
After a few hours, you should see the red water moving up the celery stalk in straight, thin lines. The colored water is traveling up the celery's capillaries. As water evaporates from the top of the celery stem, red water from the glass is pulled up into the base of the stalk. In living plants, this process goes on continuously. ,