2nd Thursday of the Month
Join Dr. Lisa Chirlian the Second Thursday of each month as we explore Kitchen Chemistry - and play Science Fact-or-Fiction; where you can win the greatest prize of all... the prize of knowledge!
Chemistry is the study of the way materials are put together and how they act under various conditions and best of all - - chemistry is ALL around us! Did you know that you have a chemistry lab right in your own home? These experiments use everyday materials and can be performed in an ordinary kitchen. Before we begin, there are some General Safety Rules to learn.
- Always be sure to have a responsible adult supervising your experiment - in fact, make Kitchen Chemistry a family experience!
- Never taste food that you are using for a science experiment - not only might it taste bad, it could also be bad FOR you.
- Finally, as a general safety precaution, never mix bleach or ammonia with anything else!
Now that you have those rules - let's learn about chemistry!
Water is an amazing substance with unique properties. We tend to take it for granted, because it is always around us—in the faucet, in the refrigerator, in the shower (and toilet!). But water’s unique properties make life, as we know it, possible on earth.
You can demonstrate water’s uniqueness quite easily. All you need is some water, an eyedropper and a penny. In this experiment you will find out how many drops of water will fit on top of a penny. And, you will do it like a scientist!
Before you start, make a prediction. How many drops do you think will fit on the penny, before they spill over? Write down your prediction.
Next—test your prediction by doing an experiment. Carefully count the number of drops that you can put on a penny without spilling over the sides. Work carefully! Try to make your drops as uniform as possible.
What did you observe? Usually people make estimates that are very low, because pennies are small and they expect that, after a few drops, the water will roll off the penny. But it doesn’t! Water is different from many other liquids because of the way its atoms interact.
It’s actually surprising that water is a liquid at room temperature. Most other molecules that are similar in size to water (like nitrogen or neon) are gasses at room temperature. The reason why water is a liquid at room temperature is that water experiences strong forces between a hydrogen atom on one water molecule and an oxygen atom on a different molecule. These interactions are called hydrogen bonds and are really specialized. They can only occur in very specific situations and water, with two hydrogen atoms bonded to an oxygen atom, is able to form many of these bonds.
The existence of hydrogen bonds helps explain why we can fit so many drops of water on a penny. The hydrogen bonds help hold the water molecules together, even when it looks like water should spill over the side of the penny.
Hydrogen bonds are responsible for a very important property of water. Everyone knows that when a lake freezes, the ice is on top of the water. For most substances, the solid form is denser than the liquid form, so the solid would sink in the liquid. Because hydrogen bonds create a network of “holes” in solid ice, it is less dense than liquid water, so it floats. This is a good thing for the fish!
Even though we can’t see hydrogen bonds (or atoms or molecules) directly, we can use science to investigate and understand their properties!
How Much Water Fits on a Penny?
- Eye dropper
1) Predict the number of drops of water that will fit on a penny without spilling over the side.
2) Add water drop by drop. Be sure to keep an accurate count.
3) Stop when the water spills over. How many drops did you get? How close was your prediction. Try it again with a nickel, dime or quarter. Is your prediction more accurate?
Things to talk about
This may seem pretty mundane, but people are usually fascinated the results. That’s what makes science fun!
- Science is everywhere.
- Studying science doesn’t have to be complicated.
- We don’t think about the science behind the behavior of everyday objects
Describe the experiment. We can “do it” on air.
- Scientists make predictions.
- Why is it important to make predictions before you do the experiment?
- Experiments need to be reproducible—keep the dropper straight up/down so drops are consistent size.
- What does it mean if your predictions are wrong?
- This experiment lets us observe the effects of things we cannot see. We can’t see the attraction between water molecules directly, but we can observe it through this experiment. If water were not so strongly attracted to itself, it would roll off the penny much sooner.
- Do you think you could make a better prediction now? How many drops do you think might fit on a dime?
- Did you notice the shape of the water on the penny, before it spilled over? It was a hemisphere. A sphere is the shape that allows the water to be close to as many other water molecules and limits the number of water molecules on the “outside” or not completely surrounded by water. (It maximizes the volume and minimizes the surface area)
Water is unusual!
- Water is unusual in having specific names—ice, water—steam—for the solid, liquid and gaseous forms of the substance. Contrast to liquid nitrogen (same name). Dry ice (solid carbon dioxide) is another material with a unique name for a different state. Most of the time, we only interact with one state (solid, liquid or gas) of a substance. This is another way that water is unique—it goes through all three states at temperatures that are close to “normal” for us.
Where else do we find hydrogen bonds?
- Rubbing alcohol (Not in nail polish remover! How are these things the same/different?)
- DNA—holds the double helix together.
How Do Straws Work? (Air Pressure)
It’s fun to drink with a straw but did you ever wonder exactly why a straw works? Straws work because of something you can’t see, but is everywhere. Sound like magic? Nope—it’s science!
Even though a glass may look empty before you fill it with your favorite cold drink, it’s actually quite full—full of gas that is. We are surrounded by the atmosphere, which is a good thing, since it contains the oxygen we need to breathe. All of that atmosphere is pushing down on us (don’t worry—we have gas inside our bodies that is pushing back, so we don’t get crushed).
What does this have to do with a straw? Well, think about what happens when you put a straw into liquid. The liquid rises in the straw, to exactly the same height as the liquid in the glass. That’s because the atmosphere is pushing down on the liquid in the glass. The atmosphere pushes the liquid in the glass up into the straw. Since the atmosphere is also pushing down on the liquid in the straw, the liquid rises, just until the force of the atmosphere on the liquid inside the straw exactly balances the force of the atmosphere inside the glass. That happens when the levels are even.
So, why can you use a straw to get the liquid up into your mouth, higher than the level in the glass? When you inhale through the straw, you take the atmosphere out of the straw (it goes into your lungs). Now the atmosphere is pushing down on the liquid in the glass, with noting the balance it inside the straw, so the liquid rises…into your mouth!
Since we can’t see the atmosphere, it’s hard to figure out how it works. Scientists deal with this problem all the time. Designing experiments to measure things that can’t be seen is a big part of a scientist’s job. Here are a few experiments you can try to see the atmosphere!
Seeing the Atmosphere
• Drinking glass/drinkable liquid
• Plastic/paper cup
• Index card that covers the entire cup.
• A tissue
• A tub or sink to work in.
1) Take a straw. Drink something from it to be sure that it works. Now, make a small hole in it (make sure the hole is large enough to see). Make sure the hole is above the level of the liquid in the glass. Does the straw still work? What happens if you cover the hole with your finger and then try to drink? When you suck on a straw that has a hole, you pull air through the hole, instead of removing air from the straw. The liquid stays put, unless you cover the hole.
2) Fill a small plastic/paper cup with water. Put the index card on top, making sure that the card completely covers the cup. Put the palm of your hand on top of the card (to hold it on) and turn the cup over. When the cup is completely upside down, take your hand away. What happens to the card? To the water? (Do this over a tub or sink, just in case!) The card remains attached to the cup. The atmosphere is pushing up with more force than the water pushes down, so the card stays attached.
3) Take a tissue. Crumple it up and place it in the bottom of a cup. If the tissue won’t stay in the bottom of the cup, use a small piece of tape to secure it. You want the tissue to be squeezed into the bottom of the cup. Turn the cup over and push it into the water. If you are careful to keep the cup level while pushing, the tissue will stay dry. Why does this happen? Even though the cup looks empty, it’s full of air. When you turn the cup over and push it into the water, the air in the cup pushes away the water and the tissue stays dry!
Separating Iron from Cereal
Many people know that iron is a necessary part of a good diet. Some foods, like breakfast cereal, have iron added, to help people get this important nutrient. But, did you know that you can actually use a magnet to see the iron in breakfast cereal? In this experiment, you will! We can get iron from food in different ways. Iron that comes from animal sources (red meat, fish, poultry) is called heme iron, and is found in a form that is similar to the way iron is used in our bodies. Iron that comes from plants is in a different form, called non-heme iron. Most fortified foods and iron supplements use non-heme iron, but some foods use actual iron metal. Yes, the same thing that is used to make nails can be found in breakfast cereal (but in much smaller bits!). Since iron metal is magnetic, you can use a magnet to see the bits of iron found in breakfast cereal. It’s easy to do, (just a little bit messy). You won’t see a lot, but you will definitely see it!
Separating Iron from Cereal Materials
• Iron fortified cereal (look for 100% of the RDA for iron on the box)
• Very warm water
• Re-sealable zipper bags
• Magnets (neodymium magnets work very well) (Caution the wet cereal may clog your drain. Discard carefully! Consider flushing it down the toilet.)
1) Put a cup or two of cereal in a zipper bag. Close the bag (leaving a very small opening for air to escapte) and crush the cereal by squeezing the bag or rolling over it with a rolling pin.
2) Add very warm water to the bag. Let the mixture sit until the cereal becomes very mushy. Add enough water to get a soupy consistency.
3) Slowly rub the magnet in small circles on the outside of the bag. It may take a few minutes, but you will see a dark spot form. The dark spot is iron. Not sure you have it? If you spot follows the magnet as you move it, you definitely have iron
Eggs are amazing! They are full of good nutrition and can be a part of every meal. Including dessert! Or course, baked goods use eggs, but did you know that you can make a cookie that is almost entirely eggs? Meringue cookies are! Just eggs, sugar and vanilla makes these scrumptious treats.
Egg whiles are slimy and runny when they are fresh from the shell. They are composed of proteins and water. The water makes them runny and the proteins give them their unique qualities. It’s the proteins in the egg whites that make meringue possible.
Proteins are very large molecules. Parts of protein molecules are attracted to water (hydrophyllic) and other parts are not (hydrophobic). In the raw egg, the proteins are folded so that the hydrophobic parts are on the inside and the parts that are attracted to water are on the outside. When the egg whites are beaten, the folding is disturbed (denatured) and, at the same time, air is beaten into the mixture. This creates a foam which can be used to make meringues.
When the foam is heated, the trapped air bubbles expand creating the light and airy cookies that taste so good! Heat also makes the foam solidify, so the cookies don’t collapse when they cool.
Meringues are easy to make with an electric mixer. Meringues can be made by hand, but it requires a strong arm! The trickiest part of making meringues is separating the eggs. It’s important to keep fat of any kind away from the egg whites because fat will interfere with the formation of the foam. Egg yolks contain fat, so keeping the yolk away from the white is critical. Fortunately, many inexpensive devices to separate eggs are availble for people who are not comfortable separating eggs by hand (just grab the yolk but make sure to clean your hands well before and after) or by dipping the yolk from one half of the cracked shell to the other and letting the white fall into a bowl.
Makes about 3 dozen cookies
3 egg whites
2 teaspoons vanilla
¼ teaspoon cream of tartar
1 cup sugar
½ cup mini-chocolate chips or finely chopped nuts (optional)
- Preheat the oven to 250oF
- Separate the eggs (save the yolks for another use)
- Combine the egg whites, vanilla and cream of tartar in a bowl.
- Beat the mixture (use a whisk attachment, if available) until it forms soft peaks. (The whisk will start to leave lines through the egg whites.)
- Gradually add the sugar (about a tablespoon at a time)
- Beat the mixture until it forms stiff peaks (a fairly stable peak forms when the whisk is removed)
- Use two teaspoons to form the cookies on an ungreased cookie sheet, or use a piping bag with a star tip for fancier shapes. Leave about 1 inch between the cookies.
- Bake for 50 minutes. Turn off the oven but leave the cookies in the oven for another 30 minutes. Remove the trays from the oven and allow the cookies to cool completely on a wire rack.
Have you ever thought about the stuff that runs out of your nose when you have a cold? That stuff is mucus, better known as snot. Even though you may only notice it when you have a cold, your nose is continuously producing mucus. While mucus can be gross, it actually serves many different and important functions in your body. This experiment will help you understand a bit more about the stuff that runs out of your nose. Mucus contains many different things, but mostly mucus is water. Mixed in with water are proteins and sugars. The model mucus that you are making will use gelatin as the protein and corn syrup as the sugar. While this is very different from the actual ingredients in the mucus in your nose, the mixture will have a very similar, familiar texture. The proteins and sugars make it stretchy and sticky. Mucus in your nose helps protect your lungs. Dust, bacteria and other particles get stuck in the mucus and don’t get any further into your respiratory system. When a lot of particles get stuck and the mucus dries up, you get a booger!
Fake Snot (Artificial Mucus)
1/2 cup very hot tap water (be careful!)
3 envelopes unflavored gelatin
1/2 cup corn syrup
- Sprinkle the gelatin on the hot water. Mix it in. (This may take a little while).
- Let the gelatin sit and cool for 20-30 minutes.
- Add about 1/2 cup of corn syrup and stir.
- As the solution cools, you can add a little bit of water (a spoonful at a time) to keep it from getting too thick.
(Note: this is not an experiment—because you can eat the results. This is a cooking project that shows how science is part of our everyday lives!)
Most people get butter from the supermarket, preformed into sticks or (sometimes) put in tubs. But, our ancestors had to make their own butter, one of the many chores of everyday life that we don’t typically have to do. But, with Thanksgiving just around the corner, it’s fun to think about doing something old-fashioned like making your own butter. It’s surprisingly easy to do!
Before we try making it, let’s think about why butter forms. You probably know that shaking cream makes butter, but did you ever wonder why? How does a liquid turn into a solid? First, think about cream. It’s full of fat but it also contains water. Usually fat (oil) and water don’t mix, but in cream, the proteins and other parts of the cream help the fat stay spread out in the water. This type of solution is called an emulsion.
What keeps the fat from clumping together? A skin surrounds bits of fat that keeps them from sticking to each other. When something breaks the skin, the fat is able to form a solid clump. In the past, butter churns were used to make larger amounts of butter, but you can make small amounts of butter just by shaking cream. Or, if you have an electric mixer, you can make as little or as much butter as you want. It’s easy!
* Heavy cream
* Leak proof jar or electric mixer/bowl
* Shake it up! (The old-fashioned way)
1. Fill your jar about halfway with cream.
2. Close the lid, making sure that the jar doesn’t leak. (Mason jars are good for this because they have an airtight seal.)
3. Shake and observe. After about 5 minutes open the jar. The cream should change form a liquid to something creamy. This is whipped cream. (You can flavor it with a little sugar and vanilla and serve it on ice cream.)
4. Shake some more. After 5-10 more minutes, you will notice a liquid forming around some solid material. The solid material is the butter; the liquid is buttermilk.
5. Strain the butter. Rinse it in water a few times, kneading it with your (clean!) hands to get rid of all the buttermilk.
6. Store the butter in the refrigerator. It will not keep as long as commercially prepared butter.
Mix it up! (The modern way)
1. Pour the cream into the mixer bowl.
2. Start mixing, using a low speed so the cream doesn’t spatter. As the cream starts to thicken, you can raise the speed.
3. Observe. After a few minutes, the cream will thicken and become whipped cream. Keep going!
4. As you continue beating the cream, notice how the texture changes. The mixture will start to look a little lumpy. If you were making whipped cream, you would want to stop before this happens.
5. After a short time, the lumps will separate, leaving a thin liquid behind. At this point you have made butter. You can rinse and knead it as described above.
Separating Dyes in Water
Sometimes, people want to know what is in a mixture. Scientists use a process called chromatography (kroh-muh-tog-ruh-fee) to separate different parts of a mixture. Dots of the mixtures—different colors of washable markers—are placed on a piece of coffee filter paper. The end of the paper is put into water. As the water moves up the filter paper, it carries the dye from the marker. Different dyes move up the paper at different rates and become separated. While this may sound very complicated, it’s actually an easy process to do at home.
Coffee Filters (cone type)
Water-soluble markers (marked washable)
1. Put a small amount of water in the bottom of a paper cup. The water should come up about one quarter inch from the bottom of the cup.
2. Cut the coffee filter paper into rectangles approximately one half inch wide by four inches long.
3. Place a small spot of marker approximately one half inch from the bottom of the paper. The spot should be above the level of the water in the cup.
4. Use a binder clip to attach the filter paper to a pencil, so that the top of the paper is attached to pencil and the bottom hangs free.
5. Place the pencil across the top of the glass so the bottom of the paper is immersed in the water. Be sure that the spot of marker is above the level of the water and that the paper doesn’t touch the sides of the cup.
6. Watch as the water moves up the paper. The spot of color will start to move up the paper as well. If the marker is a mixture of dyes, the different colors will start to separate.
Things to think about
Did the colors separate the way you expected?
Which colors separated the most? The least?
If you have several different sets of markers, try different shades of one color (greens and purples work well). Do the shades separate with the same pattern?
Keeping Gelatin From Gelling
Many people love gelatin (Jell-O is a brand name of gelatin dessert). Gelatin starts as a powder, but when it is dissolved in hot water and then chilled, it will set into a jiggly dessert treat.
If you ever read the small print, on the side of the box, you might notice you are warned not to include certain kinds of fruit, including pineapple when you are making gelatin because the gelatin will not set properly. To understand why you shouldn’t use pineapple in gelatin, you first must understand how gelatin gels.
Gelatin is made from collagen, a protein that comes from connective tissue in animals (bones and ligaments are examples of connective tissue). Proteins have very particular structures when they are in their natural setting. When gelatin is dissolved in hot water, the protein molecules are extended like a series of long strings. As the gelatin solution cools, the proteins get tangled up and trap the smaller molecules (water, sugar, flavoring) in between the protein strands, giving gelatin its distinctive, wiggly form.
So why can’t pineapple be used in gelatin? Pineapple contains an enzyme called bromelain. Bromelain is an example of a group of enzymes called proteases. Proteases are protein molecules that can chop up other proteins. (Proteases are very specific in the proteins they chop up, so they don’t chop themselves up!). If bromelain (enzyme) comes in contact with the gelatin (protein) in the hot solution, the bromelain will break down the protein into smaller pieces. These smaller pieces won’t be able to trap the water and other smaller molecules into the pockets that give gelatin its form.
Does this mean you can’t have pineapple in gelatin? No—you just have to find a way to keep the bromelain from working. Enzymes, like many proteins have a very specific shape. If the shape changes, the enzyme will not work. One way to change the shape of an enzyme is to heat it. This process is called denaturation. If you want to put pineapple into gelatin—just cook it first. Or, an even easier method is to use canned pineapple because the fruit is heated to high temperatures as part of the canning process.
- 1 box gelatin mix
- fresh pineapple
- canned pineapple
- meat tenderizer (optional—meat tenderizer is a powdered form of a protease enzyme)
- plastic cups
1) Label four cups according to what you will add: control (just gelatin mix), fresh pineapple, canned pineapple, meat tenderizer (optional)
2) Add the appropriate test material to each cup.
2) Make the gelatin according to the directions on the box. Let it cool slightly.
3) Pour one-half cup of gelatin mix into each cup.
4) Refrigerate the cups. Observe them every 20-30 minutes to see what happens. After at least four hours, take them out of the refrigerator and make your final observations.
5) If you want, make a fresh box of gelatin to eat.
Think about this! What else could you do to pineapple so it won’t prevent gelatin from gelling? Freeze it? Dry it?TOP
Dyeing Eggs with Nature
Note: this is not an experiment—because you can eat the results. This is a cooking project that shows how science is part of our everyday lives!
It’s fun to dye eggs. Many people use kits or food coloring to create brightly colored masterpieces. But, did you know that you could use vegetables to dye eggs? Yes, many plants contain compounds that are dyes. These give the plants their characteristic colors.
The dye in most plants is water-soluble. This means that you can make an egg dying solution simply by heating the vegetables in water. The dye molecules will leave the plants and end up in the water. The technical term for this process is “extraction” and is the same as process we use when we make tea from tea leaves (another plant).
Once you have created the dye, you can color the eggs simply by leaving them in the dye. If you want to be able to eat the eggs, be sure you leave them in the refrigerator while they are soaking in the dye. The longer you leave the eggs in the dye, the darker the color of the shell.
Dyeing Eggs with Foods
- Hard boiled eggs
- Red cabbage leaves, onion skins
1) Rip the cabbage leaves into small (1-2 inch) inch pieces and place in a heavy metal saucepan.
2) Cover the leaves with water.
3) Bring the water to a boil. Lower the heat and let the mixture simmer for 10-15 minutes (the water should take on the color of the leaves—this process is very similar to making tea) .
4) Allow the plant dye to cool. Add the hardboiled eggs and put them in the refrigerator. Take them out of the dye when you are satisfied with the color of the shells.
Note: this is not an experiment—because you can eat the results. This is a cooking project that shows how science is part of our everyday lives! Take care! The syrup formed in the recipe gets extremely hot. Please make this recipe as a family—with plenty of adult supervision.
Sugar is a very important part of candy. While candy is sweet, it usually doesn’t look or feel like the sugar we use to sweeten coffee or tea. Heating sugar causes it to change in many ways, including the color and texture. Careful heating turns sugar into caramel.
You can make and eat caramel by itself or you can pour it over nuts to make nut brittles. You can suck on it and it will dissolve in your mouth. Caramel is hard and brittle. But, if you add just a bit of baking soda, you can make an entirely different type of candy—still sweet but with a totally different texture.
Baking soda is a very versatile substance. It can be used in food, as a medicine and even to clean your counters. Baking soda is a leavening agent, which means it causes cakes and cookies to rise when they are cooked. Baking soda is used in the batter along with an acid (such as vinegar, lemon juice or buttermilk). The baking soda and acid react to form carbon dioxide gas. The carbon dioxide gas bubbles throughout the batter, created a light an airy texture.
Honeycomb toffee uses the same principals to make a light and airy candy. Vinegar is added to the sugar/corn syrup mixture. The mixture will become very hot when it is heated (be careful!). Observe carefully when you mix in the baking powder. Watch how the syrup changes colors and textures as the baking soda is distributed.
Honeycomb Toffee (Sponge Candy)
- 1 cup sugar
- 1 cup corn syrup (light or dark)
- 1 tablespoon vinegar
- 1 tablespoon baking soda
- 9 x 13 inch baking pan
1) Line the baking pan with foil and grease the foil.
2) Mix the sugar, corn syrup and vinegar in a medium saucepan. The mixture will bubble, so be sure the pot is large enough to hold everything!
3) Heat the sugar mixture over medium heat, stirring until the sugar melts.
4) Once the sugar melts and the mixture starts to bubble stop stirring. Cook until the mixture measures 290oF (hard crack) on a candy thermometer. The solution will be extremely hot!
5) Turn off the heat and mix in the baking soda. The mixture will lighten in color and become opaque. Do not over mix because too much mixing will deflate the bubbles.
6) Pour the mixture into the pan. Allow to cool. Break into pieces and enjoy!
Creating Tiny Sugar Crystals
(Note: this is not an experiment—because you can eat the results. This is a cooking project that shows how science is part of our everyday lives!)
Most people agree that fudge is a delicious treat. Did you ever wonder why fudge is so good? Fudge combines milk, chocolate and sugar into a creamy, mouth-watering candy. One of the reasons why fudge is tasty is its unique texture. It's smooth, creamy and almost melts in your mouth without chewing.
Fudge tastes different than a chocolate bar, even though both contain similar ingredients. The difference is due to the texture but why does fudge have such a unique texture? The answer comes from...Science!
The creamy texture of fudge comes from the size and number of sugar crystals in the candy. Sugar, of course, starts out as crystals. These crystals are large and you can see them with your naked eyes. When you put sugar into water, the crystals dissolve. Depending on what you do next, you can make sugar form large crystals, small crystals or even no crystals at all!
In many types of candy (lollipops, for example), crystals are unwanted. If crystals are present, the candy will taste grainy, not smooth and delicious. Very large crystals are needed for rock candy. Fudge requires very small (much smaller than the sugar crystals that you see in a packet of sugar) to create the unique texture of fudge.
In fudge, sugar, milk and chocolate are heated until the chocolate melts, the solution boils, and a specific temperature is reached. At this temperature, the concentration of sugar in the mixture will (eventually) form the right number of crystals to make fudge. At this temperature, the solution does not contain any crystals.
The solution is left to cool without any disruption. This is important, so that crystals don't begin to form too early. Once the appropriate temperature is reached, the solution is vigorously beaten to encourage the formation of many small crystals. Finally, the mixture is shaped and left to cool.
The traditional fudge recipe can be tricky. If every step is not followed precisely, you will get an unappetizing lump instead of delectable fudge. So, in addition to the traditional fudge recipe are two easier recipes to try.
8x8x2 inch pan, lined with aluminum foil
2 ounces unsweetened chocolate, chopped
2 cups sugar
2/3 cup half and half
2 tablespoons corn syrup
2 tablespoons butter, cut into small pieces.
1 teaspoon vanilla Pinch of salt
1. Place the chocolate, sugar, half and half and light corn syrup in a medium sized (2 quart), heavy saucepan. Light corn syrup is a different sugar (glucose) than table sugar (sucrose). The addition of a different sugar will help prevent the sucrose from crystallizing too quickly and forming large crystals. Large crystals will make the fudge grainy.
2. Place the saucepan over medium low heat. Until the chocolate melts, stir the contents gently, by scraping across the bottom of the pan with a wooden spoon. Try to avoid splashing the contents on the side of the pan. Stirring the contents will avoid the formation of hot spots that might burn. Splashing the contents on the sides might result in sugar crystals that don’t dissolve. If these fall back into the mixture, they might cause crystallization to occur too soon, later in the process
3. Once the chocolate melts, stop stirring! From this point, avoid disturbing the contents. Attach a candy thermometer to the pan. Allow the mixture to boil until it reaches 236 oF. Turn off the heat and add 2 tablespoons of butter, but do not stir! Boiling the mixture to the specified temperature makes a solution with the necessary concentration of sugar to make fudge. Leaving the mixture as undisturbed as possible prevents the formation of sugar crystals too soon.
4. Allow the mixture to cool to 110 oF. This process may take some time, probably more than an hour. Watch the temperature carefully when it gets close to 110 oF because you must not let the mixture cool too far before beating it, as described in the next step. At 110 oF, the mixture will be at the temperature that will result in the formation of lots of tiny crystals. The mixture must sit, undisturbed to be sure that crystals don't start to form too soon.
5. When the mixture has cooled to 110 oF, add 1teaspoon vanilla plus a pinch of salt. Beat the mixture rapidly until it lightens in color and thickens. This may take some time, 15 to 20 minutes, especially if you beat it by hand. (You may use an electric mixer, but be careful because it is easy to over beat the mixture. Use a low speed.). If you are unsure that you have beaten it enough, spoon a small amount into your prepared pan. If it holds its shape, it is done. Beating the mixture vigorously encourages the formation of many tiny crystals. As the crystals form, the mixture will change color because the crystals interfere with the passage of light into the mixture. The presence of crystals will also make the mixture thicken.
6. Pour the mixture into the prepared pan, using a spatula to smooth/shape it. Let it cool at room temperature and then cut it into small piece and enjoy!
Evaporated Milk, Marshmallow Cream Fudge
In this recipe, the marshmallow cream and butter coat the sugar crystals replacing the cooling and beating. The evaporated milk already has water removed so the mixture cooks more quickly. This recipe is much easier and faster than the traditional recipe.
9 x 13 x 2 inch pan, lined with foil
3 cups sugar
2/3 cup evaporated milk
4 tablespoons butter
12 ounces semi-sweet chocolate mini-chips
7 ounces marshmallow cream
2 teaspoons vanilla
Pinch of salt
1. Place the chocolate chips, vanilla and marshmallow cream in a large bowl.
2. Put the sugar, evaporated milk and butter into a large saucepan and bring to a boil over medium-low heat, stirring constantly. When the mixture boils, stop stirring and attach a candy thermometer to the pot. Allow the mixture to boil until it reaches 238 oF.
3. Pour the mixture over the chocolate mixture. Be careful—it will be very hot. Stir until the chocolate chips melt.
4. Pour the mixture into the prepared pan and allow to cool. Enjoy!
Sweetened Condensed Milk Fudge
In this recipe, the sweetened condensed milk replaces the sugar/milk mixture and requires no boiling. The chocolate and condensed milk can also be melted together in a microwave.
8 x 8 x 2 inch pan, lined with foil
14 ounce can sweetened condensed milk
3 cups semisweet chocolate mini-chips
1 teaspoons vanilla
1. Combine the sweetened condensed milk and the chocolate chips in a large saucepan. Heat over medium-low heat, stirring constantly, until the chocolate melts.
2. Add the vanilla.
3. Pour into the prepared pan.
4. Refrigerate until cool and set. Enjoy!
Keeping Apple Slices Fresh
(Enzymes in Action)
Apples make a great snack. Some people like to eat them whole and some like to slice them. If you slice your apples, and then let them sit before you eat them, you may notice they turn brown. Brown apples do not look very tasty!
Science can help explain why apple slices turn brown. Science can also help you figure out how to keep apple slices looking fresh in case you want to slice them for your lunchbox or to put in a salad.
So, why do cut apples turn brown? When picked from the tree, the apple’s skin protects the flesh. The apple skin keeps air (which contains oxygen) away from the flesh of the fruit. Oxygen is actually the reason why cut apples turn brown.
Apples contain compounds that can react with oxygen to form other compounds that are brown. Normally, these reactions occur extremely slowly. Apples contain an enzyme called polyphenol oxidase (PPO). Enzymes are molecules found in living things that make slow reactions go quickly. Enzymes catalyze (speed up) chemical reactions. PPO speeds up the formation of these brown compounds.
To prevent apples from turning brown, you can do several things. You can prevent oxygen from reaching the flesh by putting the apples in a plastic zipper bag and removing as much air as possible before sealing the bag. You can also change conditions to help prevent the PPO from effectively catalyzing the reaction.
Enzymes work best at a specific pH (amount of acid/base). By changing the pH, you can help keep your apples from turning brown. Lemon juice is an acid that can be eaten, so it’s a good choice for keeping apples looking good!
Keeping apples fresh
- lemon juice
Slice the apple and divide into two bowls. Mix some lemon juice with the apples in one of the bowls. Put both bowls aside (a warm window will speed up the change). Observe the apples every 30-60 minutes. What do you see? Feel the apples—does the texture change? Some other things to try:
You can keep oxygen from cut apples by immersing them in water. Try it! Other foods are acidic and will keep apples from browning. You can try adding pineapple juice, orange juice or even vinegar!TOP
Baking Powder, Baking Soda: What do they do?
(This is not an experiment—because you can eat the results. This is a cooking project that uses scientific principles to explain why things taste good!)
If you look at recipes for cookies, cakes or other baked goods, you will notice that they contain many similar ingredients. Flour, and sugar are found in almost all the recipes and it’s easy to understand the part they play in the cookies or cake. Flour makes up the majority of the cookie and sugar makes it sweet!
You may also notice other common ingredients. Things like salt or vanilla provide the flavoring. Most recipes also contain baking powder or baking soda and sometimes they even have some of each. Have you ever wondered what baking soda or baking powder do for cookies and cakes?
Baking powder and baking soda both help make cookies and cakes taste good. They are both leavening agents. Leavening agents are compounds that create bubbles in the batter. These bubbles expand when heated in the oven and give baked goods their nice, soft texture. (Bakers call this the “crumb”.) Why two different kinds—baking powder and soda?
Baking soda is a compound that releases carbon dioxide gas when it is combined with an acid in water. In fact, one of the other experiments on this page (“Identify Acids”) tells you how to use baking soda to find things that are acids. You can tell if something is an acid (like, for example, vinegar) because bubbles form when you mix baking soda and vinegar. Baking soda is used in recipes that contain ingredients that are acids (vinegar, buttermilk, sour cream).
What about recipes that don’t contain these acidic ingredients? Then, baking powder must be used. Baking powder contains baking soda, plus an acid (in solid form). The baking soda and acid don’t react, until they dissolve in water (or in batter!). Once the batter is mixed, bubbles start to form.
These bubbles, even though they are empty, make a big difference in the way things taste. You can test this, by using your favorite recipe. Mix up the batter without baking powder/soda and cook about half of it. Then add half the required amount of baking powder/soda and cook the rest. Observe your results. Does the baking powder/soda make it look different? Taste different?
Here is a pancake recipe, that you can use, to try this out! Cook it once as written (with baking powder). Cook it a second time, leaving out the baking powder (you can eat these, but you may not want to!). Make observations while you are cooking. Here are some things to consider:
When you leave out the baking powder:
Does the batter look different?
Do the pancakes look different while they are cooking?
Do the pancakes smell different?
Do the pancakes feel different?
Do the pancakes taste different? (taste before you add toppings!)
(makes about eight 3-inch pancakes)
3/4 cup flour
1/2 teaspoon salt
2 tsp sugar
1 tsp baking powder (omit in second batch)
1 tablespoon butter, melted and cooled, slightly
1/2 cup milk
Combine flour, salt, baking powder (if using) and sugar in a bowl, stirring with a whisk. In a second bowl, beat the egg. Stir in the butter and the milk. Mix the liquid ingredients into the dry ingredients, stirring just until combined (a few lumps are ok!). Heat a griddle or large fry pan. The pan is the proper heat when a few drops of water bounce around on the surface before evaporating. Pour the batter onto the griddle, making pancakes that are about 3 inches across. Flip them when the bottom side is done and continue cooking the second side. Enjoy with your favorite topping!
Lower the Freezing Point of Water
Try melting ice in your own freezer! We’ve had a bit of snow recently. When snow melts, it creates liquid water, which can run onto the roadways and freeze, causing dangerous conditions for drivers. To help keep the water from freezing, people put salt on the roads. You may have wondered why they do this.
Salt, when dissolved in water, causes the freezing point of water to become lower. Another way to say this is that water will remain a liquid at temperatures below 32F (0C). So, if the temperature is 20F, roads that would typically be icy, can just be wet (which is still slippery, but not nearly as slippery as ice). For the same reason, when salt is placed on top of ice, it causes the ice to melt. You can do an experiment at home, to demonstrate this principle. You can also see how the amount of salt affects the freezing point of water.
• Small disposable/plastic cups (bathroom cups work well).
• Table salt (Kosher salt works too)
• Measuring cup
• Space in a freezer
• Thermometer (optional, make sure it goes down to around 0F)
1) Decide how many different samples you want to try. This will probably depend on the amount of free space you have in your freezer.
2) Decide how much salt you are going to put in each sample. If you can fit four samples in your freezer, you might try the following (all in two ounces of water):
• no salt
• 1/4 teaspoon salt
• 1/2 teaspoon salt
• 1 teaspoon salt
Label your cups so you can easily identify them later on. Don’t depend on remembering where you put them in the freezer. Sometimes things get moved around, unintentionally.
3) Make your solutions. Measure 1/4 cup of water and add the appropriate amount of salt. It’s easiest to mix the salt and water in a larger cup and then pour it into the smaller cup for the freezer.
4) Make some observations. Do the solutions look different? If you’d like, you can measure the temperature of the solutions at this time.
5) Put your samples in the freezer. Note the time (or set a timer) and check them every 30 minutes. Observe your samples every 30 minutes. Which ones start to freeze more quickly? Do the samples freeze solidly? How low does the temperature go?
6) You can try this with other things you find in your kitchen. Sugar and baking soda are fun to try.TOP
(Note: this is not an experiment—because you can eat the results. This is a cooking project that shows how science is part of our everyday lives!)
Caramel is a gooey treat that is part of many kinds of candy and desserts. While the recipes may all be different, they are all based on caramelized sugar (melted sugar). When you heat sugar (sucrose) crystals, the sugar begins to melt. Once it melts it breaks apart into to smaller sugar molecules (glucose and fructose). These smaller sugars undergo complex reactions, which cause the color of the solution to change from clear to the familiar caramel color. In fact, caramel is sometimes used as a food coloring—look for caramel color on food labels.
You can caramelize sugar at home on your stove or in the microwave. Making caramel on the stove can be a little tricky, but the microwave makes it easy. Be very careful—the sugar gets very, very hot. Protect your hands and any surfaces where you might put the caramel.
- 1/2 cup sugar
- 1/4 cup light corn syrup
- 2 cup Pyrex measuring cup (be sure to use Pyrex, or something similar—the sugar gets too hot for regular glass)
- A metal cookie sheet, lined with aluminum foil
1) Mix the corn syrup and the sugar in the Pyrex measuring cup. Make sure all the sugar is moistened.
2) Put the mixture in the microwave. Microwave for one minute and then check the solution. Is it bubbling? Has the color started to change from white to clear to tan? (The exact time this takes will depend on your particular microwave oven.)
3) Continue to microwave for one-minute intervals, checking for bubbling and color changes after each minute. Once the mixture starts to darken, remove it from the microwave and place the measuring cup on a hot plate (or other heat safe spot). The color will continue to deepen, even after you remove the cup from the microwave. BE CAREFUL—the syrup is extremely hot!
4) Let the mixture sit for a few minutes, until the color stops changing. If you would like a darker caramel, you can put the cup back in the microwave for 10-15 seconds. Once the color is to your liking, pour the caramel onto the prepared cookie sheet.
5) Let the caramel cool. Once it is cool, you can break it by banging the caramel and cracking it into bite sized pieces.
6) You can eat the caramel once it is cool. Note: this caramel is hard, like a lollipop. Soft caramels also include other ingredients like butter or cream.
Why do you add corn syrup?
If the sugar happens to turn back into crystals, the caramel will taste gritty, instead of smooth. Mixing in some corn syrup helps to make sure that crystals don’t reform.TOP
Ice Cream, Ice Cream!
Ice cream is a great summertime treat. You probably buy ice cream from the supermarket, but ice cream is pretty easy to make at home. You don’t need a fancy machine, either. You can make your own ice cream with some simple household items. And, at the same time, you can explore some science!
The recipe for vanilla ice cream is simple—half and half, sugar and vanilla are mixed together to make the ice cream base. But changing these three things into a tasty dessert requires a little scientific know-how. You can’t just put the base into the freezer and get ice cream. The liquid will freeze and become a solid but it won’t have the familiar texture of ice cream. The water in the cream will freeze more quickly than the rest of the half and half and you will get an icy mess!
To get everything to freeze together with the familiar, delicious texture of ice cream, you must make sure that the base is mixed continuously while it is freezing, so that the fat and liquid particles stay together. You also want to be sure that the mixture freezes quickly. The faster the mixture freezes, the smaller the ice crystals. Small ice crystals make the ice cream taste smooth and creamy!
- 1/2 cup half and half (or 1/4 cup heavy cream and 1/4 cup milk)
- 1 tablespoon sugar
- 1/2 teaspoon vanilla
- 2 quart size zipper top plastic bags
- 1 gallon size zipper top freezer bag
- 4-5 cups of ice
- 1/4 cup coarse (Kosher) salt
- Thick gloves or a thick towel (to use while handling the ice)
1) Place the half and half, sugar and vanilla in one of the quart size zipper top bags. Shake gently until the sugar dissolves.
2) Carefully squeeze as much air from the bag as possible. Seal the zipper top. This step is important because excess air in the bag can make force open the zipper top and the cream mixture will spill out.
3) Place the bag with the cream mixture into the second, quart size bag. Remove the air from the second bag and seal it. The second bag will help keep the ice/salt away from the cream mixture, keeping the ice cream tasty!
4) Place the ice into the gallon size zipper top bag and add the coarse salt. Put the bags containing the cream mixture on top of the ice/salt in the bag. You can use a thermometer to verify that the temperature of the ice/salt mixture is below the normal freezing point of water (32oF). Remove as much excess air as possible from the gallon size bag and seal it.
The bag will get very cold—use thick gloves or wrap the bag in a thick towel before you handle it!
5) Make the ice cream. Shake or roll the bag so the ice and ice cream base are constantly moving. In approximately 10 minutes, you will have ice cream! Carefully remove the quart size bags from the ice. Be sure to keep the salt/ice mixture away from the ice cream!
The ice cream may be soft. You can eat it now (if you like soft ice cream) or you can put the quart size bag into the freezer until the mixture hardens completely.
Why does this work?
The added salt lowers the freezing point of water. The ice/salt mixture can get colder than 0oF and freezes the ice cream mixture quickly. The quicker the freezing, the smaller the ice crystals formed in the ice cream. Small ice crystals are important because, when the crystals are large, they ruin the smooth texture that we all like in our ice cream.
Shaking the ice cream mixtures also helps keep the ice crystals small and also helps keep all the components of the milk/cream mixture together.
Do It Yourself!
How long till the ice cube melts?
Design your own experiment and learn about research and the scientific method. It’s summertime and the weather has been really hot. Ice cubes help keep things cool on these hot summer days, but they also melt really quickly. You may have wondered, how can I make ice cubes last longer?
You might not realize it, but just by thinking about keeping ice cubes frozen, you’ve started using the scientific method. Keep going and you can design your own experiment and even develop a theory! All from ice cubes.
The scientific method is a general way of designing experiments to help us understand how the world works. I’ll describe how to use the scientific method to investigate how to select a cup to help keep ice cubes frozen longer (which will help keep your drink colder, longer). You can give it a try and you can also design your own questions to answer.
Ice cubes and whatever else you need to do your experiments (cups, a kitchen scale, thermometers, timers, etc. may all be useful) Apply the scientific method!
1) Make an observation. The first part of the scientific method is to notice something about the world around you. Good scientists are always on the lookout for interesting, unusual or confusing things.
2) Ask a question. (Develop a hypothesis) Think about your observations—what questions could you ask about them? It might be helpful to create a question that begins, “I wonder...”
3) Design the experiment. This is the fun part! You get to figure out how you are going to test your hypothesis and answer your question. When you design an experiment, the most important thing to remember is—only change one thing! If you want to see if ice melts faster by a window or in a dark closet, on the location should change. Try to keep everything else (the amount of ice, the type of container that holds the ice) the same. Why is it so important to only change one thing? Well, if more than one thing changes, it’s hard to know which thing had more of an effect. For example, if you put a small amount of ice in a paper cup by a sunny window and a larger amount of ice in a plastic cup in a dark closet, the smaller amount ice in the paper cup by the sunny window would probably melt first. But, you wouldn’t be able to tell if that was because of the location, the type of cup, or if it just takes less time for a smaller amount of ice to melt.
4) Think about (analyze) the results. What happened when you did your experiment? What do the results of your experiment say about your hypothesis? If the results of the experiment agree with (support) your hypothesis, then you are done! If not, think about using the results of your experiment to ask a new question. Once you ask a new question, you can back to step 3, and repeat the process with a new experiment. Scientists call this kind of circling back an iterative process.
5) Share your results. Scientists write papers that explain their experiments and results. They publish these papers in scientific journals, so other scientists can see and understand the results. Other scientists may try to reproduce the results to check the work or they may use the results to help in new research. You can share your results with your friends or family. You can tell them about your experiment or you can make a poster that shows what you did. If you really feel ambitious, you can write your own scientific paper.
6) Think about something new to try. When scientists finish one experiment, they don’t stop—they try to figure out how they can explore even further. Think about how you can do more experiments and learn even more!
Here’s what I did:
1) Make an observation. I have noticed (observed) that different types of materials are used for drinking cups—glass, plastic, paper, Styrofoam, for example. I have also noticed that hot drinks are more likely to be put Styrofoam cups, and that Styrofoam cups feel cool on the outside, even with a hot drink inside.
2) Ask a question. (Develop a hypothesis) I wonder if Styrofoam cups would keep things colder and keep the ice from melting longer than plastic or paper cups.
3) Design the experiment. • I went to the supermarket and bought 16 ounce Styrofoam and clear plastic cups. • I made fresh ice cubes using the icemaker in my kitchen freezer. (I used fresh ice cubes because they are all similarly sized when they first come out of the icemaker). • I weighed the each ice cube before I started. Each weighed 1.5 ounces. • I put an ice cube into each cup and put the cups on the kitchen counter. • I checked the cups every 15 minutes to see if they melted. I soon realized that it was going to take much longer for the ice to melt, so I started checking every 30 minutes, until one of the cubes was mostly melted, then I checked every 5 minutes, until it melted completely. • After 2 hours and 35 minutes, the ice in the plastic cup was completely melted. The ice cube in the Styrofoam cup had not completely melted—0.75 ounces remained.
4) Think about (analyze) the results. My results agreed with my hypothesis. The Styrofoam cup did keep the ice cube colder so they didn’t melt as quickly as the ice cube in the plastic cup.
5) Share your results. I’m sharing the results with you!
6) Think about something new to try. Would the ice cube last longer if the cup was covered? Does crushed ice melt faster than cubes? Do ice cubes last longer in clear plastic cups or in colored plastic cups? The possibilities are endless!TOP
Eggs are good to eat. But eggs can also teach us science. Here are two experiments that you can do with eggs. Remember—even though eggs are food, you should not eat the eggs that you use for these experiments! Eggshells are made of a chemical—calcium carbonate. You can perform a chemical reaction and make the calcium carbonate dissolve. This may sound messy, but eggs actually have a membrane between the shell and the white/yolk that will remain after the shell dissolves. (You can see this membrane when you peel a hard boiled egg.)
The membrane surrounding the egg has a special property. It will allow small molecules (like water) to pass through it, but it keeps large molecules like proteins and fats (the white and the yolk) inside. This process is called osmosis. You can observe this process using the shell-less eggs, water and corn syrup.
Disappearing Egg Shells
• Container large enough to hold eggs
1) Put some eggs in the jar/container. Add enough to completely cover the eggs. What do you see? Bubbles will start to form on the eggs. Cover the container and place it in the refrigerator.
2) Check your eggs after 12-24 hours. What has happened? Carefully remove the eggs from the container and gently rinse them under running water. If some eggshell still remains, put the eggs back into the container and add fresh vinegar. Check the eggs again after another 12-24 hours.
3) When the shell is all gone, make some observations. Carefully hold the egg and notice how it feels. Hold it up to a light—what do you see? With an adult helper, working over the sink, see what happens if you gently squeeze the egg.
Disappearing Egg Shells, Part Two
• Shell-less eggs (3 or more)
• 3 containers
• Corn syrupFood coloring (optional)
1) Label the containers ‘water’, ‘corn syrup’ and ‘control’. Place an egg in each container.
2) Cover the egg labeled ‘water’ with water. Add food coloring, if you’d like. Cover the egg labeled ‘corn syrup’ with corn syrup. If you want use food coloring, add it to the corn syrup before you pour the corn syrup over the egg. Leave the egg in the control container alone.
3) Put the eggs in the refrigerator for at least 6 hours.
4) Carefully remove the eggs from their containers and observe them. What has happened to each egg? Use the uncovered egg (the control) to remind you what each egg looked like before you put it in water or corn syrup. Try putting the egg from the corn syrup into water for a few hours. What happens?
Why does this work?
Eggshells are made of a chemical called calcium carbonate. Calcium carbonate is a base. Vinegar is another name for a chemical called acetic acid which is (of course!) an acid. Acids and bases react with each other. In this case, the reaction makes new chemicals that are soluble in water so the eggshell dissolves. The reaction also creates carbon dioxide gas. If you looked carefully when you put the eggs into the vinegar you probably noticed small bubbles forming. These are carbon dioxide bubbles.
Once the eggshell dissolves, the white and yolk are held in a membrane. Scientists call this membrane semi-permeable because only some things can pass through it. It will allow small molecules (like water) to pass through it, but it keeps large molecules like proteins and fats (the white and the yolk) inside. This process is called osmosis.
In osmosis, the water molecules move from the area with more water molecules to the area with fewer water molecules. The inside of the egg is mostly, but not all water (about 90% water). When you put the egg into pure water, some of the water molecules from the solution move into the egg and the egg swells up. You can tell this happens easily if you use food coloring because the egg will change color. You can also observe that the egg is slightly bigger than the untreated egg.
Corn syrup is only about 25% water. When you put an egg in corn syrup, water will move out of the egg and it will appear shriveled. If you use food coloring in the corn syrup, you may wonder why the egg turns color, if the water is flowing out of the egg. This happens because, while most of the water molecules flow out of the egg, after some time passes, water molecules pass into the egg at the same rate as they are flowing out. This is called a dynamic equilbrium.
If you want to try something else, take the egg that was in the corn syrup and put it into water. What do you think will happen? This picture may give you a clue!TOP
Marshmallows are a soft, chewy, sugary treat. Marshmallows are mostly made from sweeteners (a combination of sugar and corn syrup), which is why they are so sweet. Marshmallows also contain gelatin, which gives them their chewy consistency. What you won’t find on the ingredient list is air—that’s right—air is important for good marshmallows. When marshmallows are made, air bubbles are created during the mixing process, and these air bubbles give marshmallows their puffiness. You can use these air bubbles, and a little science to make marshmallows change size.
Expand Marshmallows by Making a Vacuum
• Glass or thick plastic bottle
• Drinking straw
1) Put some marshmallows in the bottle.
2) Use the clay to seal the top of the bottle. Poke a hole in the clay and put the drinking straw through it. Seal the hole by pressing the clay up against the straw
3) Suck on the straw to remove the air from the bottle. Watch the marshmallows carefully! They will begin to expand as the air is removed. If you have trouble seeing the marshmallows expand, watch what happens when you stop sucking on the straw. The air rushes back into the bottle and the marshmallows will contract immediately. It’s easier to see this because it happens suddenly
Expand Marshmallows by Heating
Be careful—the marshmallow gets very hot!
1) Put a marshmallow on a paper plate and place it in the microwave oven.
2) Set the timer on the microwave oven for 30 seconds (start with this time and make it longer, if necessary)
3) Watch what happens! (This is a dramatic demonstration) Take the marshmallow out of the oven and watch what happens as it cools off. Be very careful, the marshmallow will be extremely hot.
Fun With Ice
Here’s a magic trick you can do to amaze your friends! You can lift an ice cube without tying any knots! Unlike most magic tricks, which use illusions, this one uses science.
Magic Trick Materials
Salt (in a shaker works best)
1) Put the ice cube on a plate. Put a little bit of water on top of it.
2) Cut a piece of string (about 6 inches long). Put one end of the string in the water on the ice cube. Show everyone that the string is not attached to the ice cube.
3) Sprinkle a little salt on top of the ice cube. If you want to be mysterious, you can tell everyone that it is magic powder. If you want to be scientific, you can explain that the salt will melt a little bit of the ice so the string sinks into the cube. Then the coldness of the cube will refreeze the water around the string.
4) Wait a minute or so (it’s a good idea to practice this beforehand, so you know how long it will take). You will probably be able to see the string sink into the ice a little bit.
5) Once you feel confident the string is in the cube, pick it up and amaze your friends!
Why does this work? (And another experiment to try)
Almost everyone knows that water freezes (or melts) at 32oF (0oC). That’s a physical constant, which means that under normal conditions, water always freezes or melts at this temperature. But, we can do something to change the melting point of water. In the winter ice forms on roads and sidewalks, making travel slippery and dangerous. When the temperature is below 32oF (0oC), ice will not melt by itself. To make it melt, people put salt on the ice. Adding salt to the ice lowers the freezing point of the ice (now an ice-salt mixture).
You can see this for yourself, with this easy experiment.
Materials for observing the change in freezing point:
Insulated cup (Styrofoam or double walled travel mug—a regular cup will work, just not as well)
Thermometer (Be sure you have one that can read temperatures below freezing!)
1) Fill your glass, about 2/3 full, with ice. Add cold water, leaving some room at the top (so you can stir the solution).
2) Wait a few minutes (keep stirring gently) and then measure the temperature. It should be 32oF(0oC). If it is not, you may need to either wait a little longer or add more ice.
3) Add salt to the ice/water solution. You will need to add a lot (1/4 to 1/2 cup, or more, depending on the size of your cup). You want the solution to be very salty.
4) Wait a few minutes and measure the temperature again. How low did it go?
5) If the temperature of the solution only went down a few degrees, add more salt and measure again!TOP
Last month I explained how to grow sugar crystals to make candy. This month, we are also going to grow crystals only we are going to make them look like snowflakes. Snowflakes are crystals of water. Since water needs to be kept cold to stay solid, you can’t really use water crystals to make things to keep inside.
You need to use other compounds, which are solid at room temperature (like sugar) to make things to keep. For this experiment, we are going to use borax. You can find borax in the laundry aisle of many supermarkets. One brand names is 20 Mule Team. Caution: This experiment uses boiling water which is very hot. Please be sure to have a responsible adult supervising. Also, be sure to wash your hands after working with borax and keep the snowflakes away from small children or pets that might try to eat them!
1 cup boiling water
2-3 tablespoons borax
Shallow pan or jar
1) Create your borax solution. Boil one cup of water. Little by little, stir the borax into the water (about a half tablespoon at a time). Keep stirring until no more borax will dissolve.
2) Create your snowflake form. Cut a pipe cleaner into three pieces and twist them together in the middle. If you want to grow your snowflake in a jar, make one piece longer so you can attach it to a pencil and hang it into the jar.
3) Put your snowflake form(s) into the jar or pan. Pour the borax solution on top. Put them in a place where you can check on them daily.
4) When your snowflakes have grown, take them out and let them dry. If you hang them near a sunny window, they will sparkle!
Things to Think About and Do
- Look at the crystals with a magnifying glass. Compare them to the borax powder you started with... do they look similar or different?
- Can you grow other kinds of snowflakes? You can try this same experiment with sugar, table salt or Epsom salts. Which grows the biggest snowflakes?
Growing Sugar Crystals
This is not an experiment—because you can eat the results. This is a cooking project which shows how science is part of our lives—even candy! Sugar is a solid. Each little grain or crystal of sugar is made up of lots of individual sugar molecules. The molecules are arranged in a very orderly fashion that gives sugar its shape. Rock candy is made of sugar crystals. The crystals grow bigger than the ones you find in a packet of sugar or the sugar you buy to make cookies. They’re easy to grow—just give it a try! Caution: The sugar/water solution is extremely hot. Please take care when mixing and pouring it.
Remember—you’re going to eat the results—don’t use anything that you wouldn’t use for food preparation)
3 cups sugar
1 cup water
Clean jars or tall glasses
Clean string, straw or popsicle stick
1) Get your crystal growing apparatus ready. You need to suspend your string into the container without it touching the sides or bottom. If you are using a string, you can tie it to a pencil and then lay the pencil across the top of the jar like shown in this image.
Wet your string and dip it into sugar so that a few crystals cling to the string. This will give your candy a place to start growing.
2) Put three cups of sugar in the pan and add 1 cup of water. It will seem like there is too much sugar/not enough water, but it will be ok! Put the pan on the stove and heat the sugar/water solution. Stir it gently. As the solution heats up, more and more sugar will dissolve. The solution will look cloudy. You want to heat it until the solution turns clear and starts to bubble. Be Very Careful—the solution is very hot. Let it cool for 5-10 minutes before proceeding.
3) Pour the solution into the jars. Be sure the string is not touching the sides or bottom. Growing crystals takes time because the crystals grow as the water evaporates. Cover the top with a paper towel or coffee filter to prevent dust from getting into the jar. Put the jar some place where it won’t be disturbed.
4) Check on your crystals every day. If a crust of crystals forms across the top of the jar, just remove it with a fork or spoon so water can continue to evaporate. If crystals form on the sides/bottom of the jar, pour the solution into a clean jar and place the string into the clean jar.
5) When your candy is big enough, you can take it out and eat it. If you want to save it, just let it dry and then store it in a closed container. It won’t spoil, but if you leave it out, it may attract bugs! Enjoy!TOP
Watching an Enzyme Work
Plants and people need lots of chemistry to live! Our bodies are chemical plants using food and oxygen in chemical reactions to do all the wonderful things we do every day. Our bodies use special molecules, called enzymes to make these reactions go smoothly and quickly.
Catalase is a common enzyme. It helps change peroxides (which are created in other reactions and aren’t good for living things) into water and oxygen. It does this very quickly. Most living tissue contains catalase. We can use potatoes to help see catalase work because bubbles of oxygen form when we put potatoes into hydrogen peroxide. We can also see how to stop enzymes from working.
When potatoes are cooked, the structure of the enzyme changes and it doesn’t work. Cooked potatoes won’t make bubbles of oxygen. Even though catalase is present in living things, the amount may vary. Apples contain very little catalase . Putting apples in peroxide causes only a few bubbles to form.
Hydrogen Peroxide (available in the first aid section of most pharmacies or supermarkets)
A small pot (for cooking some of the potato)
1) Label the cups: a. Hydrogen peroxide plus raw potato b. Water plus raw potato c. Hydrogen peroxide plus cooked potato d. Hydrogen peroxide plus apple
2) Cut small pieces of potato. Leave some raw. Boil some pieces for 5-10 minutes (until they are soft)
3) Cut small pieces of apple.
4) Put a small amount of hydrogen peroxide or water (as labeled) into each cup.
5) Add raw potato to the cup with hydrogen peroxide and the cup with water. What happens in each cup?
6) Add cooked potato to the cup with hydrogen peroxide. Does it behave like the raw potato?
7) Add the apple to the hydrogen peroxide. Do you see any bubbles? Look carefully, especially around the apple pieces.
8) Try this! Put other fruits or vegetables into the peroxide (try carrots, mushrooms, grapes or zucchini). Which ones make lots of bubbles?
Making a Lava Lamp
You probably have seen Lava Lamps in stores. These lamps plug into the wall and can get rather warm. They contain materials that are unsafe to use at home. Here's a simple way to make a lava lamp using materials you can find in your kitchen.
A clear bottle
food coloring (optional)
Fill the water about two-thirds full of water. Add a drop or two of food coloring, if you want. Pour about an inch or two of oil on top of the water and let the oil settle on top of the water. Pour a stream of salt on top of the oil and watch your lamp go! Keep adding salt to keep the lamp moving.
Making Glue from Milk
Most people buy glue at the store to use when they need to stick things together. Store bought glue is convenient, but for fun, you can make your own glue from milk. It’s fun and it’s easy.
Just follow these steps.
Skim milk (do not use whole or 2% milk)
Coffee Filter Paper (cone type works best)
Mix 1 cup of milk and ¼ cup of vinegar. Let the mixture sit for 10-15 minutes. The milk will separate and small pieces of a white solid will form. This white solid is some of the proteins in milk (casein) and will end up becoming the glue.
Place the coffee filter paper over a tall glass. Pour the milk/vinegar mixture into the filter. Pour a little bit at a time so the mixture doesn’t overflow the filter. Make sure the bottom of the filter is above the level of liquid in draining into the glass. Let the filter sit for 10-15 minutes so most of the liquid is removed.
Pour the solids into a clean bowl or plastic container. Add two teaspoons of baking soda to the solids and mix. Listen carefully—you will be able to hear the baking soda react with the extra vinegar and you may even see the some bubbles. Add about one teaspoon of water and mix. You’ve made glue. Now try it out on some paper!
Why does it work?
Milk is a suspension—solids are suspended in the liquid (not dissolved like in salt water). When you add vinegar (an acid), some of these suspended solids (the protein, casein) change their shape and can no longer be suspended. The casein forms the gloppy solid that is filtered from the liquid. Baking soda (a base) is then added to neutralize the acid and change the protein back into a shape that is more fluid. This becomes the glue. Water can be added to give the glue whatever consistency you would like. TOP
Finding Starch Around The Kitchen
Starch is a part of many foods we eat. It’s not always easy to know what foods contain starch. Sure, cornstarch is easy to identify because it has starch in the name. But does sugar contain starch? Does flour? Here’s a fun way to find out.
First, go to your local drugstore and get some iodine solution. Iodine is sold as an antiseptic (cleans things) and can usually be found in the first aid section. Ask your local pharmacist if you can’t find it.
Then, gather up some foods from your kitchen. Remember, when doing science in the kitchen—never, ever eat the food you are using and keep your work away from surfaces where food is prepared. The sink can be a good place to work.
Put a little bit of each food in a small disposable cup. If you prefer, you can put several types of food on a disposable plate. Be sure to leave enough room between the different samples.
Look at the iodine solution. The color ranges from orange to brown, depending on how much you have in your container. Place a few drops of iodine on each sample. If the sample doesn’t contain starch, the iodine solution will remain the same orange/brown color. But, if the sample contains starch, the iodine solution will turn purple/black in color.
After you test all your samples, try to figure out what starch containing compounds have in common. Do they come from animals or plants? Do they come from certain parts of an animal or plant? You might decide to analyze some new, different foods to figure it out.
Slime can be made using white glue and borax (found in the laundry detergent section of most supermarkets). When you make slime you start with a polymer (the glue). Polymers are molecules that form in long chains. The borax links the individual chains together and changes the properties of the glue.
If you make slime, ask yourself what happens to the slime when you stretch it by pulling your hands away from each other? What happens to the slime if, instead of pulling your hands away from each other, you pull one hand toward your body and push the other hand away?
Make a saturated Borax solution
• Add 1 tablespoon of Borax to 1 cup of water.
• Stir well. If you have a jar or other suitable container, shake the mixture.
• The borax will settle to the bottom, at first, but with stirring will create a cloudy solution. It’s OK if a little borax remains—you are creating a saturated solution, which means that you have the maximum amount of borax, dissolved.
Prepare the glue solution
• Measure ½ cup of glue
• Add ½ cup of water, stir to combine
• Pour ½ cup of the glue/water mixture into a Ziploc bag.
• Food coloring may be added now (if you want colored slime!)
• Put some of the Borax solution into a cup.
• Add a bit of the Borax to the glue (you can start with about ¼ cup). Seal the bag and knead the mixture gently.
• Add more Borax (up to ½ cup) until the slime has the right consistency.
• When you are finished, tTake the slime out of the bag and have fun!
In the book, "Bartholomew and the Oobleck" by Dr. Seuss, the king of Didd wishes for something different to fall from the sky than rain or snow. Though no one is prepared for a sudden shower of Oobleck! Now you can make your own magical messy Oobleck at home.
Oobleck is similar to slime except it is made from cornstarch (also a polymer) and water. Investigate ooblek’s properties and try to decide if it is a solid or a liquid!
* 2 cups of cornstarch
* 1 cup of water
* Green food coloring
* Sheet of wax paper
Mix together the cornstarch, water, and food coloring in a bowl. Pour a little onto the wax paper so you can play with it. Roll it between your hands and it feels solid, but let it sit and it becomes a gooey liquid.
Using Baking Soda To Find Acids
Some of the things we find in kitchens are acids. Acids are found in foods that taste sour. Here is a way to use baking soda to identify acids in the kitchen. When baking soda is mixed with an acid, bubbles of carbon dioxide form. If baking soda is mixed with a base or a neutral (neither an acid nor a base), no bubbles form.
* baking soda
* water milk
* fruit juices (for example, lemon, pineapple, orange, apple)
* liquid soap
* several small cups
Place about a teaspoon of baking soda in each of the small cups. Add some of each liquid to the baking soda. If bubbles form, you've found an acid!
Making An Acid/Base Indicator
With Cabbage Juice
Baking soda can only identify acids. You can use cabbage leaves to make an indicator (a substance which changes different colors in acids or bases). Cabbage juice is bluish and turns red in acids and green in bases.
* a few red cabbage leaves
* fruit juices (for example, lemon, pineapple, orange, apple)
* liquid soap
* Milk of Magnesia
* several small cups (clear cups work best)
Rip the cabbage leaves into small pieces. Place in a pan and cover with water. Heat the water until it boils and then turn down the heat. Let the cabbage leaves simmer for 10-15 minutes. Let cool. Strain the leaves out of the juice. Put the juice in each of the small cups. Add some of each liquid to the cabbage juice and watch the color change!
Making Invisible Ink
You can make several different kinds of invisible ink in the kitchen. Lemon juice and milk both become visible when heated. A solution of baking soda and water becomes visible when grape juice is painted over it.
* lemon juice
* baking soda dissolved in water
* purple grape juice
* white paper
Use a Q-tip to write a secret message with lemon juice. Let it dry. Get an adult to help you go over the paper with a warm iron. The message will appear in brown. Try the same thing with milk. Use a Q-tip to write a secret message with the baking soda solution. Let it dry. Paint over the message with grape juice. The grape juice will change color and show your message.
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