Every object on earth, whether it’s a boat, a person on a bike, or two forks attached to a toothpick, has a single point called the center of gravity (or center of mass) which gravity acts on. This fun trick demonstrates how you can balance the mass of two forks and a toothpick sitting on the edge of a wineglass. The center of gravity on a curved glass exists in the space between the glass and the forks! Amazing!
If you light the toothpick inside the glass on fire, it will burn out when the flame hits the cooling glass. Because the toothpick is so light (has very little mass), the center of gravity doesn’t change much, so the forks remain balanced.
(Adapted from Kitchen Science Lab for Kids)
Grab an extra bag of cranberries this Thankgiving! Kids can use it to reveal invisible messages they write with baking soda and water.
-around 2 cups of cranberries
-small paintbrush, Q-tip, or lollipop stick
Safety tips and Hints:
Boiling the berries should be done by an adult. Keep the lid on the pan, since the air pockets that make cranberries float can also make them explode. Kids can take over once the juice is cool.
When playing with cranberry juice, aprons or old clothes are a good idea, since it stains!
Step 1. Cut a cranberry in half and observe the air pockets that make it float.
Step 2. Boil the cranberries in about three cups of water for 15 to 20 minutes, covered. Listen for popping sounds as the air in the cranberries heats up and they explode.
Step 3. Crush the cooked berries and push the liquid through a sieve or colander to collect the concentrated cranberry juice.
Step 4. Allow the juice to cool and pour it into a casserole dish or cake pan big enough to hold a piece of paper. If your cranberry juice seems thick and syrupy, add a little water, so that it’s thin enough to soak into paper!
Step 5. Test the paper you want to use by cutting a small piece and soaking it in the cranberry juice. If it stays pink, it will work, but if it turns blue or gray, try some other paper.
Step 6. Add a few teaspoons of baking soda to 1/3 cup of warm water and stir well. Don’t worry if you can still see some baking soda.
Step 7. Using a Q-tip, paintbrush, or a homemade writing tool, use the baking soda solution as ink to write a message on your paper. It may take a little practice, so don’t get frustrated.
Step 8. Let your message air dry, or speed things up with a blow dryer.
Step 9. To reveal your message, place your paper in the cranberry juice and see what happens!
*What other natural acid/base indicators could you use to do this experiment? What else could you use as ink.
The Science Behind the Fun:
Cranberries contain pigments called anthocyanins (an-tho-SY-a-nins,) which give them their bright color. In nature, these pigments attract birds and other animals to fruit. This is important because animals eat the berries and spread plants seeds from one place to another.
These pigments, called flavanoids, change color when they come in contact with acids and bases. Cranberry juice is very acidic, and the pigment is pink in acids, but when you add it to a base, it turns purple or blue.
Baking soda is a base, so your baking soda message will turn blue when it comes into contact with the pigments in the cranberry juice. Eventually, when enough cranberry juice soaks into the paper, it will dilute the baking soda, turning the pigment back to red and your message will disappear!
There are over 300 kinds of anthocyanins which are found in many fruits and vegetables including blueberries, red cabbage, grapes and blueberries. Scientists believe they may have many health benefits.
As a kid, I was always fascinated by stories of pieces of straw from a field being driven into wooden planks in barns and houses by the swirling winds.
With a potato, plastic drinking straws and a glass of water, you can see for yourself how this happens. Like drinking straws, real straw is hollow and although a potato is much softer than a piece of wood, you’ll get the picture.
You’ll need a potato and some sturdy plastic drinking straws.
Begin by soaking a potato in a glass of water for about 30 minutes to soften the skin. We used a red, boiling potato, because that’s what I had on hand.
Then, grasp a straw tightly, near the middle and stab it into the potato as hard as you can. Try starting at different distances from the potato to see whether it makes a difference in how far the straw goes in. (You can mark it with a Sharpie and pull it out.)
We were surprised to find that, instead of breaking or bending, the straw can be driven surprisingly deep into a potato . This happens because objects in motion, like the straw, tend to stay in motion and objects at rest, like the potato, tend to stay at rest. (Newton’s First Law of Motion) This is called inertia. In addition, the paper-thin edges of a drinking straw don’t offer much resistance, and potatoes are composed of around 90% water.
To make a holidays version of the fizzing bath tablets in the video, we scented them with pumpkin pie spice and added a little more oil to incorporate the extra ingredients.
1 cup baking soda
¼ cup cream of tartar
3 Tbsp. coconut oil, melted to liquid
1 tsp. pumpkin spices
-Whisk together baking soda, cream of tartar and pumpkin spices. Slowly drizzle in coconut oil, mixing immediately. Stir for several minutes until you get a nice even mixture that holds together when you press it between your fingers. Add a little more oil if it is too powdery.
-Add a few drops of food coloring and mix again until the color is incorporated.
-Press the bath bomb mixture into a tablespoon and tap in on a tray to remove the bath tablet. If they don’t hold together, try adding a little more oil and mixing again. Dry the bath fizzies on a plate or cooking sheet and package them in cellophane bags or pretty baking cups for friends and family. Use the fizz bombs within a few weeks for maximum fizziness!
You can make larger “bath bombs” using molds for round ice cubes (which we found at Target.) Double or triple the recipes, gently press some mixture into each side of the mold, and mound a little extra on each side. Press the mold together to compress the bath bomb mixture into a single ball. Tap one side gently with the back of a spoon and gently open the mold to release that side of the sphere. Hold it in your palm and repeat with the other side to release the entire bath bomb from the mold.
The science behind the fun: The chemical name for baking soda is sodium bicarbonate , and cream of tartar is an acid called potassium bitartrate, or potassium hydrogen tartrate . When you mix them together in water, you create a chemical reaction that forms carbon dioxide gas bubbles! It’s interesting to note that at temperatures below 76 degrees F (25 C), coconut oil is a solid, but that at temperatures above this, it melts into a clear liquid. How does this affect your bath fizzies? Will they work in cold water as well as they do in warm water? Try it!
Thanksgiving isn’t the same without cranberries. This year, pick up an extra bag for this fun science experiment.
With cranberries and baking soda, you can create invisible messages that will be revealed to friendly eyes and self-destruct before your enemies have a chance to read them. You’ll see how some pigments in fruit can change color when they’re exposed to an acid or a base. *I discovered that some paper will turn blue in cranberry juice, so test the type of paper you want to use by first dipping a small piece it in the cranberry juice (before you start writing messages!) It should turn pink, not blue. Otherwise, you won’t be able to see your message!
-half a bag of cranberries
-a homemade pen: To write your message, you’ll also want to find a small paintbrush, Q-tip, or something else with an absorbent tip. We had the best luck using cake-pop sticks or cotton swabs cut in half (non-cotton end) as pens.
Have an adult or teenager boil the cranberries in about three cups of water for 15 or 20 minutes. Be sure to put a lid on the pan, since the small pockets of air that help cranberries float can make them explode as they cook. If you listen, you’ll hear some of the them popping! Crush the cooked berries and push the liquid through a sieve or colander to collect the concentrated cranberry juice. Most cranberry juice from the grocery store is diluted with water, corn syrup and other juices and won’t work as well!
Let the juice cool and pour it into a casserole dish or cake pan that the paper you’re writing your messages on will fit into. If your cranberry juice seems thick and syrupy, add a little water (maybe half a cup.) It has to have enough water in it so that it will soak into the paper!
To make your invisible ink, add a few teaspoons of baking soda to about 1/3 cup of warm water and dissolve it as well as you can. Don’t worry if you can still see some baking soda. Using your homemade writing tool, use the baking soda solution to write a message on your paper. It may take a little practice, so don’t get frustrated. You’ll get the hang of it!
Let your message air dry, or speed things up with a blow dryer.
To reveal your message, float and then submerge your paper in the cranberry juice and see what happens!
The science behind the fun:
Cranberries contain pigments called anthocyanins (an-tho-SY-a-nins), which give them their bright color. In nature, these pigments attract birds and other animals to fruit. This is important because animals eat the berries and spread plants seeds from one place to another.
These pigments, called flavanoids, change color when they come in contact with acids and bases. Cranberry juice is very acidic, and the pigment is red in acids. When you add it to a base, it turns purple or blue. Baking soda is a base, so your baking soda message will turn blue when it comes into contact with the pigments in the cranberry juice. Eventually, when enough cranberry juice soaks into the paper, it will dilute the baking soda and make the paper acidic, turning the pigment back to red and your message will disappear!
There are over 300 kinds of anthocyanins which are found in many fruits and vegetables including blueberries, red cabbage, grapes and blueberries. Scientists think they may have many health benefits and some researchers are even making organic solar cells using flavanoids!
Enrichment: What other juices can you use to reveal secret messages? What else could you use as ink? If you use lemon juice as ink, does it turn a different color?
Try making your own recipe for spy juice! I’d love to hear how red cabbage works! Check out my red cabbage litmus paper experiment to find out how to make red cabbage juice.
Ever wonder how much starch is in your Thanksgiving dinner? Click here for a fun experiment that lets you test your favorite foods for starch using iodine from the medicine cabinet.
Remember to supervise small children if you do this experiment, since iodine should not be ingested! Happy Thanksgiving!
Grab an extra bag or two of cranberries and you can stir up a Thanksgiving science project: Spy Juice and invisible ink!
Click here for detailed directions.