NOT A DROP TO DRINK
Almost all of the water on Earth is in the oceans. This means that it is very salty. Is there any way to remove the salt so fi that the water is drinkable?
Yes! Salt can be separated from ocean water through a process called distillation. To distill water, you boil it. The water leaves the container in the form of steam, but since salt has a much higher boiling point, it stays behind. The steam is piped through a filter and into a condensing vessel. By this time, the steam has cooled, so it begins to condense into liquid water. This water is salt-free.
Water can also be separated from salt through evaporation. The Great Salt Lake in Utah and the Dead Sea in Israel have salt formations along their shorelines that have formed through evaporation.
Observation 5
Add a few pinches of salt to 1¼ cup (60 Ml) of water, and stir vigorously until all the salt has dissolved. Pour the saltwater solution into a large flat pan, and place the pan in a warm place where it will be undisturbed for a few days. (During the winter, you can place it on top of a radiator.) Eventually, all the water will evaporate, and the salt will be left behind. You will see a white material on the bottom and sides of the pan.
ROCK CANDY
You can use what you have just learned to make something everyone likes—candy. All you need are water and sugar—another supermarket staple. Experiment 9 is the recipe, I mean scientific procedure, for making rock candy.
EXPERIMENT 9
Materials
Water
A small pot
A 2-cup (480-mL) Pyrex measuring cup
Sugar
A metal spoon
Bamboo skewers
Procedure
1. Fill the pot with water and bring it to a boil.
CAUTION: Be careful not to burn yourself.
2. Add approximately 1 cup (240 mL) of hot water into the measuring cup.
3. Begin adding sugar to the hot water; add 1 tablespoon (15 mL) at a time. Continue to add sugar until the water is completely saturated. (You'll know it is saturated when you can no longer make the sugar dissolve.)
4. Rub sugar on the bamboo skewers.
5. Place the bamboo skewers in the cup of water. Make sure they remain upright.
6. Allow the water to cool.
Results
As the water cools, the sugar will come out of solution, and sugar crystals will form on the bamboo skewers. The crystals will keep on forming until the water reaches room temperature and the solution stabilizes. When you take the bamboo skewers out of the water, you will have rock candy.
Chapter Four
Pasta, Macaroni, Spaghetti, C and Other Noodles
EDDIE: My uncle left me a farm that's 8 inches (20 cm) wide and 20 miles (32 km) long.
RICHARD: What do you grow on a farm with such a strange shape?
EDDIE: Spaghetti!
According to a story passed down to us over the years, Marco Polo—a great explorer from Venice, Italy—traveled to China, ate Chinese noodles, and brought the idea back to Italy. If that story is true, we should salute Marco Polo every time we eat pasta.
The word "pasta" is used to describe noodles made of semolina. The term may also be used to describe meals that are prepared using the noodles. Semolina is made from durum wheat. The wheat is processed to create a granular substance that contains large quantities of an elastic protein called gluten.
Commercial pasta manufacturers mix semolina with water, then force the mixture through metal plates with specially shaped holes. If the plates have round holes, the result is spaghetti. To make flat pasta like linguine or lasagna noodles, the mixture is pushed through thin slots. Once the dough has been shaped, it is dried, then packaged.
When eggs are added to the mixture, the result is egg noodles. Green pasta is usually produced by adding spinach juice.
Pasta Name Shape
Farfalloni Large butterflies
Fusilli Spindles
Lancette Little spears
Riccioline Little curls
Spaghetti Little strings
Vermicelli Thin spaghetti
If you like really fresh pasta, you can buy a small pasta machine and make spaghetti, linguine, or lasagna noodles at home.
You cook pasta by boiling it in water. The longer you cook pasta, the softer it gets. If you want it firm and chewy (al dente), you should cook it for about 5 minutes. If you like softer pasta, you should cook it for 8 to 10 minutes. Uncooked pasta will stay fresh for about 6 months.
Chapter Five
The Soda Aisle
Who has not craved a tall glass of soda on a hot, sticky summer day? Soda is a solution of water and various other ingredients. These solutes—substances that are dissolved in another substance— include carbon dioxide, sugar or artificial sweeteners, various flavorings, and food coloring. The carbon dioxide gives soda its fizz.
OBSERVATION 6
Pour some seltzer or club soda (unflavored soda water) into a glass. Place the glass and the bottle of club soda in the refrigerator. When 3 hours have passed, taste the soda in the glass. Pour a new glass of soda from the bottle and drink some. Does it taste different? Most of the carbon dioxide has escaped from the first glass, so it should taste similar to tap water.
IT'S ALL ABOUT PRESSURE
My cousin Sidney was always arguing with his brother-in-law Hy. When closing a plastic soda bottle, Sidney would always squeeze the bottle, leaving the smallest amount of air space possible. He said that decreasing the volume of air space increased the pressure in the bottle. As a result, the soda would remain carbonated (fizzy) longer. Hy disagreed vehemently. Who was right? Experiment 10 will provide the answer.
EXPERIMENT 10
Materials
Two unopened bottles of club soda
Two large plastic glasses
A refrigerator
Procedure
1. Place both soda bottles in the refrigerator for about an hour, so they can reach the same temperature.
2. Pour 1 cup (240 mL) of soda from each bottle into a glass.
3. Squeeze one bottle until the air space above the soda is as small as possible. Screw the cap on tightly.
4. Screw the cap of the other bottle tightly, but do not squeeze the bottle.
5. Place both bottles in the refrigerator for 24 hours. (It would be a shame to let the soda you just poured out of the bottles go to waste! Slowly add some chocolate syrup to a glass of milk. When the chocolate syrup has settled to the bottom of the glass, add the club soda. Stir the mixture vigorously with a spoon. You will notice that the foam on top stays white while the milk turns brown. Enjoy your egg cream!)
6. When 24 hours have passed, open the bottles and sample the soda. Do they both seem to fizz the same? Do they taste the same?
7. Repeat the experiment, leaving the bottles in the refrigerator for 12 hours. Does varying the time change the outcome?
8. Try the experiment without refrigerating the bottles. Any differences?
Results
The fizziness of soda depends on the amount of carbon dioxide dissolved in it. The amount of carbon dioxide dissolved in a container is influenced by the temperature of the liquid, the pressure in the container, and how easily the carbon dioxide reacts with the other ingredients in the soda.
In general, more carbon dioxide is dissolved in cooler liquids. The greater the pressure in the container, the more likely carbon dioxide will remain dissolved in a solution. When carbon dioxide reacts easily with other ingredients, it is more likely to remain dissolved.
Because a bottle is squeezed to reduce the amount of free space inside, the pressure will be greater, and less carbon dioxide will leave the solution. Therefore, the squeezed bottle should be fizzier.
DIET VS. REGULAR: WHICH WEIGHS MORE?
Diet soda has fewer calories than regular soda because it contains artificial sweeteners rather than sugar. Is the number of calories the only difference between diet and regular soda? Try Experiment 11 to find out.
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p; EXPERIMENT 11
Materials
A can of Diet Pepsi™ and a can of Pepsi™, or a can of Diet Coke™ and a can of Coke Classic™
A sink filled with water
A kitchen scale
Procedure
1. Place a can of regular soda and a can of diet soda in the water-filled sink. Which can floats higher in the water? Why do you think that happens?
2. Weigh each can on a kitchen scale and record the weight. Is there a difference in the weights? Record the difference.
3. Read the labels on the cans. Do they contain the same amount of soda? If so, can you explain any differences in their weight?
Results
The only difference between the diet and regular sodas is the sugar content. The regular soda contains natural sweeteners, such as sugar or corn syrup. The diet soda contains an artificial sweetener, usually NutraSweet®. The generic name for NutraSweet is aspartame.
Aspartame is hundreds of times sweeter than sugar. As a result, diet soda contains a much smaller amount of sweetener than regular soda does. The difference in the weight of the cans is a pretty fair estimate of the amount of sugar or corn syrup in the can of regular soda.
Observation 7
To get an idea of how much sweetener is in regular soda, place a paper cup on a kitchen scale. Weigh the cup and record your results. Add sugar to the cup, one level teaspoonful at a time, until the weight on the scale matches the weight difference you calculated in Experiment 11 plus the weight of the paper cup. How many teaspoonfuls of sugar did you add?
To test the accuracy of this method, measure out 118 cup (30 mL) of sugar and weigh it on the kitchen scale. Add the sugar to 1 cup (240 mL) of cold water. Stir the water until all the sugar dissolves. Weigh the sugar-water solution.
Taste the sugar-water solution. Now, slowly add Equal®—an artificial sweetener that contains NutraSweet —to 1 cup (240 mL) of cold water. Stop adding Equal when the mixture tastes as sweet as the sugar-water solution. Weigh this cup. The difference in weight should be about equal to the amount of sugar you added.
Chapter Six
Cleaning Supplies
SOAP: A BRIEF HISTORY
At one time, soap was used strictly for medicinal purposes. About 1,800 years ago, a famous Greek doctor named Galen was the first healer to recommended using soap for cleaning the body. About 1,300 years ago, an Arab scholar named Geber (Jabir ibn-Hayyan) tried to convince people of the importance of washing with soap.
Despite the efforts of these men, soap still didn't get much attention. In the 1600s, it was popular among the upper-class to give soap as a gift. The soap was usually accompanied by instructions for its use. Even in the early 1900s, few people bathed more than once a week. People must have been very "aromatic" back then.
Soap was originally made from animal fats and ashes from wood fires. A soap recipe from around the time of the United States Civil War included lard (soft, white, solid fat from a hog), sal soda (a form of the chemical sodium carbonate), stone lime (a form of calcium carbonate, which is also used to make chalk).
The soda and lime were dissolved in a long, labor-intensive process that involved bringing the ingredients to a boil in a copper or brass kettle, allowing some ingredients to settle out, and then pouring off the liquid. Lard was added, and the mixture was brought to a boil again. The mixture was poured into dishes or molds. When it cooled, it was cut into bars. Today, getting soap is much easier. You can just buy it at the supermarket.
EXPERIMENT 12
Materials
Really dirty hands
A sink
A bar of soap
Procedure
1. Rinse your hands in warm water. Examine them to see how much dirt is left.
2. Scrub your hands really well with soap and water. While you're scrubbing, look at the soap bubbles. Do they look gray or black? If so, dirt is suspended in the foam.
3. Rinse your hands under hot water.
Results
Washing your hands with soap gives much better results than just rinsing them with water. This is because the molecules in soap can mix with the oil on your skin and wash it, and the dirt, away. Read the next section to learn more about how soap works.
HOW SOAP CLEANS
When you sweat, a mixture of oils and water cools your body. The water evaporates into the air, leaving the oil behind. Over time, the oil builds up and traps flakes of old skin, dirt, and bacteria.
If you rinse your skin with water, the oils will not be washed away, because oil and water do not mix. To remove the oil and the dirt it contains, you must use soap. The same oil-and-dirt mixture often stains your clothes, so they too must be washed with soap to get really clean.
All soaps are surface active agents, or surfactants. They can act simultaneously on two types of substances. That's because every molecule of a soap has two parts. One end is hydrophobic (from the Creek words hydro meaning "water," and phobic meaning "fear"). This end cannot dissolve in water. The other end of each molecule is hydrophilic (from the Greek words hydro meaning "water," and philic meaning "loving"). This part has a strong affinity for water.
When you wash your hands or your clothing, the hydrophebic end of each soap molecule latches onto the oil and the dirt the oil contains. The hydrophilic end latches onto the water. As a result, the oil drops stay suspended in the water and can be easily washed away.
OBSERVATION 8
Place a bar of Ivory™ soap and a bar of any other brand of soap in a sink full of water. What happens? The Ivory soap will float, while almost every other brand will sink. This happens because Ivory soap is less dense than water. The water buoys it up so much that it does not sink. The other soap sinks because it is not as buoyant and is more dense than water. Why do you think this happens?
Here's a secret that the makers of Ivory soap would probably prefer that you did not know. Their manufacturing process includes a blending stage that forces air into the Ivory soap mixture. The added air changes the density of the bar of soap, so it floats. (It also makes it look as if you are getting more soap than you really are.)
PURE OR PURE MALARKEY?
Procter & Gamble, the company that makes Ivory soap claims that the soap is 99.44 percent pure. Have you ever wondered exactly what this means?
In the late 1800s, Procter & Gamble hired a scientific expert to evaluate Ivory soap and competitors' soaps. The expert decided that a pure soap should consist of nothing but fatty acids and alkalies. According to this definition, Ivory was almost completely pure. Its only "impurities" consisted of 0.11 percent uncombined alkalies, 0.28 percent carbonates, and 0.17 percent mineral matter. Ever since these tests were conducted, Proctor & Gamble has stated that its product is 99.44 percent pure on every package. Most other brands cannot make the same claim.
It is important to keep in mind that this claim is really just a marketing ploy. A different expert might include other items soothing oils, perfumes, and antibacterial agents—in his or her definition of a pure soap. If these items were considered "pure," then other soaps might be able to make similar claims.
DETERGENTS
Even though soap has been used for centuries, it is not an ideal cleaner. Soap can react with the minerals dissolved in "hard" water to form a residue commonly called soap scum. This residue can cause a ring around the bathtub, a dull finish on hair, and yellow spots on clothing.
In the 1930s, scientists developed detergents-soap substitutes that do not react with the minerals in hard water. Today, most laundry-cleaning products contain detergents. Examples include Tide™, WiskT™, and Fab™. Another benefit of detergents is that they are effective in hot, warm, and even cold water. Soap works best in hot water.
EXPERIMENT 13
Materials
12 pieces of cloth from an old, clean T-shirt
Soil
Butter or margarine
Peanut butter
A bar of soap
Laundry detergent
Hot wate
r
Cold water
Procedure
1. Ask permission to rip up an old, clean T-shirt.
2. Stain the twelve pieces of cloth as follows: rub four pieces in soil collected outside, wipe a little butter or margarine on four pieces, and put a dab of peanut butter on four pieces.
3. Separate the stained cloth pieces into four groups. Each group should have one sample of each type of stain.
4. Wash one group in hot water and soap, one group in hot water and detergent, one group in cold water and soap, and one group in hot water with no soap or detergent.
Results
There are no right or wrong answers. The stain left on each piece of cloth will depend on the temperature of the water, the amount of agitation, the type of surfactant used, and the type of stain.
Nearly everyone uses laundry detergent to clean his or her clothes. Since one brand of detergent is not much different from all the others, how well it sells has a lot to do with how it is marketed and advertised. Clever, memorable commercials with catchy jingles can generate huge sales.
Science Lab in the Supermarket (Illustrated) Page 3