Sodium alginate (Say it like you say algae!) is a substance found in the cell walls of brown algae, including seaweeds and kelp. Its rubbery, gel-like consistency may be important for the flexibility of seaweed, which gets tossed around on ocean waves.
Here on dry land, you can use sodium alginate to make edible balloon-like blobs that are liquid in the middle. We can thank scientists for this delicious project, since they discovered that a chemical reaction between sodium alginate and calcium causes the alginate to polymerize, or form a gel. In this experiment, the gel forms on the outside of a sodium alginate blob, where the chemical reaction is taking place. The inside of the blob remains liquid!
No heat is required for this experiment, making it safe and fun for all ages!
Sodium alginate and calcium lactate can be tricky to find at the grocery store, so you’ll probably have to order them online. But they’re not very expensive, and you’ll have lots of fun playing with them!
-a blender or hand blender (parental supervision required for small children)
-1/2 tsp sodium alginate
-2 tsp calcium lactate
-flavored drink drops, like Kool-Aid or Tang (optional)
-squeeze bottle or syringe for popping boba*
You can make these with juice, but if there is any calcium in the juice, you may end up with foam in your blender, since it may start to polymerize the sodium alginate when you blend it in.
- Add 1 and 1/2 cup water (or calcium-free juice) to the blender.
- To the water, add 1/2 tsp. sodium alginate.
- Blend for about a minute, and let rest for 15 or 20 minutes, or until the bubbles are gone.
- If you want to add flavor, divide the sodium alginate solution into small containers and stir in the flavor, like a squirt of Kool-Aid liquid.
- Add 4 cups of water to a clean, clear glass bowl or container.
- To the water, add 2 tsp. calcium lactate and mix until completely dissolved. This is your calcium lactate “bath.”
- To make edible water balloons, fill a spoon, like a tablespoon, with the sodium alginate solution, and slowly lower it down into the calcium lactate bath. You’ll see a gel begin to form. Gently turn the spoon so the sodium alginate falls off the spoon and into the calcium lactate.
- After about 30 seconds, you’ll be able to see a pale blob in the water. Leave it there for three or four minutes. You can make several edible balloons at once.
- When the blobs are ready, use a spoon to carefully remove them from the bath and put them in a clean bowl of water for a few seconds to rinse them off.
- Put your edible balloons on a plate and taste them. What do you think?
- *To make popping boba, add the fruit-flavored sodium alginate to a squeeze bottle or syringe. Drip the flavored sodium alginate into the calcium lactate as fairly large drops. It may take some practice to get uniform drops of the size you desire. When they’re solid enough to remove from the calcium lactate, rinse them gently and add them to your favorite drink. A small sieve works well for rinsing.
Now that you know how to polymerize sodium alginate with calcium, what else could you try? Can you make a foam in the blender? Can you make gummy worms in the bath using the rest of your sodium alginate solution? Can you invent something entirely new??? Try it!
Thank you to Andrew Schloss’s book Amazing (Mostly) Edible Science for the experiment inspiration! Adding the Kool-Aid and Tang drops to add a little flavor and color was our idea! (This blog post was first published on KitchenPantryScientist.com on May 3rd, 2016 and revised to add popping boba July 24th, 2018.)
Take your summer food game up a notch using… science! Sorbet recipe below. Vinaigrette recipe is in the post below this one.
Simple Freezer Strawberry Sorbet (adapted from Epicurious.com)
30 minutes hands-on prep time, 8 hours start to finish
*Parental supervision required for boiling sugar syrup
a shallow dish
1 quart strawberries
1/3 cup lemon juice
1/3 cup orange juice
1 cup sugar
2 cups water
What to do:
- Make a sugar syrup by bringing 1 cup sugar and 2 cups water to a boil in a heavy sauce pan. Boil for 5 minutes.
- Puree strawberries in a blender or food processor until smooth.
- Add strawberries, lemon juice and orange juice to the sugar syrup.
- Pour mixture into a shallow dish and cool for 2 hours in the refrigerator.
- Put the chilled sorbet mix in the freezer for 6 hours, stirring every hour.
- Enjoy your sorbet!
The Science Behind the Fun:
In sorbet, sugar acts as an antifreeze agent, physically getting in the way of ice crystal formation to keep crystals small, so that you don’t end up with one big chunk of ice. Pre-chilling the mixture before freezing it allows it to freeze faster, which also encourages smaller crystals to form.
“When I wasn’t at school, I was experimenting at home, and became a bit of a Mad Scientist. I did hours of research on mayonnaise, for instance, and although no one seemed to care about it, I thought it was utterly fascinating. When the weather turned cold, the mayo suddenly became a terrible struggle, because the emulsion kept separating, and it wouldn’t behave when there was a change in the olive oil or the room temperature. I finally got the upper hand by going back to the beginning of the process, studying each step scientifically, and writing it all down. By the end of my research, I believe, I had written more on the subject of mayonnaise than anyone in history. I made so much mayonnaise that Paul and I could hardly bear to eat it anymore, and I took to dumping my test batches down the toilet. What a shame. But in this way I had finally discovered a foolproof recipe, which was a glory.” Julia Child, from My Life in France
Julia’s secret for fool-proof mayo? Beat the mixture over a bowl of hot water to get the oil and eggs to form an emulsion, which is a mixture of two thing which are normally immiscible, like water and oil. In an emulsion, a bunch of one type of molecule will actually surround individuals or small groups of the other type of molecule (think ring-around the rosy with one or two people in the middle who would rather not be there.)
When you’re trying to make an emulsion, it also helps to add a mediator called a surfactant to get between and interact with the immiscible molecules to stabilize the mixture. In a vinaigrette prepared using oil, mustard and vinegar, the proteins in the mustard act as surfactants.
To make delicious vinaigrette:
- Using a fork or wire whisk, mix together: 1 Tbsp. vinegar and 1 Tbsp. mustard.
- Add 3 Tbsp. oil (olive, vegetable or your favorite), drop-by-drop, whisking until you see an emulsion form! You can tell when an emulsion begins to form, because the mixture will start to look lighter-colored and thicker as the molecules are rearranged and reflect light differently!
Try some variations on these kitchen experiments. Does it work better to use a cold egg, room temperature egg, or warm egg? What happens if you try to make mayo by setting your mixing bowl in a bowl of ICE water? Do you get an emulsion?
When whipping up mayonnaise, adding a little water to the eggs before adding the oil helps make some of the proteins in the eggs more available to act as surfactants. Of course, adding a little mustard helps too and tastes great!
Here’s the New York Times recipe we used to make mayonnaise:
- 1 large egg yolk, at room temperature
- 2 teaspoons lemon juice
- 1 teaspoon Dijon mustard
- 1/4 teaspoon kosher salt
- 1 teaspoon cold water
- 3/4 cup neutral oil such as safflower or canola
- In a medium bowl, whisk together the egg yolk, lemon juice, mustard, salt and 1 teaspoon cold water until frothy. Whisking constantly, slowly dribble in the oil until mayonnaise is thick and oil is incorporated. When the mayonnaise emulsifies and starts to thicken, you can add the oil in a thin stream, instead of drop by drop.
As Julia Child would say, “Bon Appetit!”
Looking for fun, creative summer projects? I showed off some projects from STEAM Lab for Kids this morning on WCCO MidMorning!
It’s hard to believe that my new book “STEAM Lab for Kids” is already in the Amazon book store! I studied both art and science in college, so this one was SO much fun to write!
Last summer, my publisher made a few videos of projects from the book for me to share with you. Here’s the first one, which features some sugar science!
More than just art-forward science, tech, engineering and math projects, my new book STEAM Lab For Kids introduces young learners to #STEAM visionaries including Louis Pasteur , Johannes Kepler, Katherine Johnson, Camille Claudel, August Rodin, Benoit Mandelbrot, Ada Lovelace and M.C. Escher. Each chapter introduction includes words on how art and STEM have influenced #STEAM role models like Sophie Shrand of Science with Sophie, neuroscientist and violinist Kaitlyn Hova, engineer and film maker Joyce Tsang, graphic artist-turned TV producer Christian Unser and musician Matt Wilson! Here’s a peek at one of the projects…
There are few gifts more fun than a homemade science kit. Give a kid a bottle of vinegar and a box of baking soda and you’ll make their day. Throw in a bottle of Diet Coke and some Mentos mints, and you may be their favorite person ever. Make a kit for your kids or grand kids. Make one for your favorite niece or nephew. Encourage kids to make kits for friends and siblings.
Here are some ideas for items to include in your kit.I’ve highlighted links to the experiments on my website (just click on the blue experiment name) in case you want to print out directions to add to your kit. You can also find these experiments on my Kitchen Pantry Scientist YouTube channel!
-composition book: Makes a great science notebook to draw, record, and tape photos of experiments into.
-clear plastic cups to use as test tubes and beakers
-measuring spoons and cups
-school glue (white or clear) for making Mad Scientist’s Slime
-contact lens solution for making Borax-free Slime
-gummy worms to transform into Frankenworms
-baking soda: Can be used for a number of experiments like fizzy balloons, magic potion . Or just mix with vinegar to make carbon dioxide bubbles.
-vinegar Great for fizzy balloons , alien monster eggs and magic potion.
-balloons for fizzy balloons.
-dry yeast for yeast balloons.
-white coffee filters: can be used for magic marker chromatography, in place of a paper bag for a coffee-filter volcano or making red cabbage litmus paper.
-cornstarch:Lets you play with Cornstarch Goo, a non-newtonian fluid. Here’s the video.
-marshmallows with rubber bands and prescription bottle rings you have around the house can be used to make marshmallow catapults. My kids used theirs to make their own Angry Birds game.
-Knox gelatin and beef bouillon cubes can be used to make petri plates for culturing microbes from around the house. You can also use the gelatin for cool osmosis experiments!
-food coloring Helps you learn about surface tension by making Tie Dye Milk. Here’s the video. You can also easily make colorful sugar-water gradients that illustrate liquid density!
-Mentos mints will make a Mentos geyser when combined with a 2L bottle of Diet Coke.
-drinking straws are great for NASA soda straw rockets and a carbon dioxide experiment.
To take it up a notch, throw in a copy of one of my book! You can find them on Amazon, Barnes and Noble and anywhere else books are sold!
Crying over broken candy canes? Cry no more. Make art!
My publisher recently sent me a copy of “Amazing (Mostly) Edible Science,” by Andrew Schloss. There are tons of fun experiments in the book, but Candy Cane Origami seemed like a perfect one to try during the holidays.
*Melted candy can get dangerously hot, so parental supervision is required!
-candy canes (broken or whole), wrappers removed
-heavy-duty aluminum foil
-a cookie sheet
-a wire cooling rack
What to do:
- Preheat oven to 250F.
- Cover cookie sheet with foil
- Place candy canes on foil, not touching each other
- Bake candy canes for around 10 minutes and have an adult check them. They should be stretchy, but not too hot to touch.
- When the candy canes are ready, bend, fold, twist and pull them into cool shapes. Try pulling one long and wrapping it around a chopstick to make a spiral. What else could you try?
- If the candy gets to brittle to work with, put it back in the oven for a few minutes to make it soft again.
The science behind the fun:
If you looks at the ingredients of candy canes, they’re usually made of table sugar (sucrose), corn syrup, flavoring, and food coloring. Glucose and fructose are sweet-tasting molecules that stick together to make up most of the sugars we eat, like table sugar (sucrose) and corn syrup. You can think of them as the building blocks of candy.
At room temperature, candy canes are hard and brittle, but adding heat changes the way the molecules behave. Both table sugar and corn syrup contain linked molecules of glucose and fructose, but corn syrup has much more fructose than glucose, and the fructose interferes with sugar crystal formation. According to Andrew Schloss, “the corn syrup has more fructose, which means the sugar crystals in the candy don’t fit tightly together. The crystals have space between them, which allows them to bend and move without cracking.”
Here’s a great article on the science of candy-making!
If you’re looking for holiday gifts for a science-loving kid, my books Kitchen Science Lab for Kids and Outdoor Science Lab for Kids include over 100 fun family-friendly experiments! They’re available wherever books are sold.
Gelatin is the substance that makes Jell-O jiggle. See what happens when food coloring molecules move, or DIFFUSE through Jell-O.
This creative science experiment that my kids and I invented lets you play with floatation physics by sprinkling glitter on melted gelatin, watch colorful dyes diffuse to create patterns and then use cookie cutters to punch out sticky window decorations. Water will evaporate from the gelatin, leaving you with paper-thin “stained glass” shapes.
-plain, unflavored gelatin from the grocery store or Target
–a drinking straw
*You can use the recipe below for two pans around 8×12 inches, or use large, rimmed cookie sheets for your gelatin. For a single pan, cut the recipe in half.
Step 1. Add 6 packs of plain, unflavored gelatin (1 oz or 28 gm) to 4 cups of boiling water. Stir well until all the gelatin has dissolved and remove bubbles with a spoon.
Step 2. Allow gelatin to cool to a kid-safe temperature. Pour the liquid gelatin into two large pans so it’s around 1-1.5 cm deep. It doesn’t have to be exact.
Step 5. In the pan with no glitter, use a straw to create holes in the gelatin, a few cm apart, scattered across the surface. It works best to poke a straw straight into the gelatin, but not all the way to the bottom. Spin the straw and remove it. Then, use a toothpick or skewer to pull out the gelatin plug you’ve created. This will leave a perfect hole for the food coloring. Very young children may need help.
Step 6. Add a drop of food coloring to each hole in the gelatin.
Step 7. Let the gelatin pans sit for 24 hours. Every so often, use a ruler to measure the circle of food coloring molecules as they diffuse (move) into the gelatin around them (read about diffusion at the bottom of this post.) How many cm per hour is the color diffusing? Do some colors diffuse faster than others? If you put one pan in the refrigerator and an identical one at room temperature, does the food coloring diffuse at the same rate?
Step 8. When the food coloring has made colorful circles in the gelatin, use cookie cutters to cut shapes from both pans of gelatin (glitter and food coloring), carefully remove them from the pan with a spatula or your fingers, and use them to decorate a window. (Ask a parent first, since some glitter may find its way to the floor!) Don’t get frustrated if they break, since you can stick them back together on the window.
Step 9. Observe your window jellies each day to see what happens when the water evaporates from the gelatin.
When they’re dry, peel them off the window. Are they thinner than when you started? Why? Can you re-hydrate them by soaking the dried shapes in water?
The Science Behind the Fun:
Imagine half a box filled with red balls and the other half filled with yellow ones. If you set the box on something that vibrates, the balls will move around randomly, until the red and yellow balls are evenly mixed up.
Scientists call this process, when molecules move from areas of high concentration, where there are lots of other similar molecules, to areas of low concentration, where there are fewer similar molecules DIFFUSION. When the molecules are evenly spread throughout the space, it is called EQUILIBRIUM.
Lots of things can affect how fast molecules diffuse, including temperature. When molecules are heated up, they vibrate faster and move around faster, which helps them reach equilibrium more quickly than they would if it were cold. Diffusion takes place in gases like air, liquids like water, and even solids (semiconductors for computers are made by diffusing elements into one another.)
Think about the way pollutants move from one place to another through air, water and even soil. Or consider how bacteria are able to take up the substances they need to thrive. Your body has to transfer oxygen, carbon dioxide and water by processes involving diffusion as well.
Why does glitter float on gelatin? An object’s density and it’s shape help determine its buoyancy, or whether it will float or sink. Density is an object’s mass (loosely defined as its weight) divided by its volume (how much space it takes up.) A famous scientist named Archimedes discovered that any floating object displaces its own weight of fluid. Boats have to be designed in shapes that will displace, or push, at least as much water as they weigh in order to float.
For example, a 100 pound block of metal won’t move much water out of the way, and sinks fast since it’s denser than water. However , a 100 pound block of metal reshaped into a boat pushes more water out of the way and will float if you design it well!
What is the shape of your glitter? Does it float or sink in the gelatin?
Here’s a video I made for KidScience app that demonstrates how to make window gellies
Credit: My 11 YO daughter came up with the brilliant idea to stick this experiment on windows. I was just going to dry out the gelatin shapes to make ornaments. Kids are often way more creative than adults!
Gallium is a soft metal related to other metals in Group 13 of the periodic table, including aluminum. It doesn’t exist as a free element in nature, but can be purified from other metallic ores, like zinc. Each gallium atom has 31 protons in its nucleus, so its atomic number is 31.
You’ll find it around you in thermometers, semiconductors, and even some LED lights, and one property that makes it so cool is that it melts from solid to liquid at low temperatures (around 85.6 degrees F or 29.8 degrees C.) This makes it easy to play with the liquid metal simply by melting it in a glass of hot water, or in the palm of your hand.
*Not for small children! Wearing gloves and safety goggles is recommended when observing gallium. Although is is fairly safe, gallium will coat hands with a lead-like substance. (Wash with soap and water to remove.) Gallium can also damage other metals, so keep it away from jewelry, like rings. I always recommend doing your research, as well as checking out the MSDS (Material Data Safety Sheet) of a new substance before using it to know what precautions to take.
We ordered 99.99% pure gallium on Amazon. It arrived in plastic tubes,in crystal form, but by placing the tubes in hot tap water, it melted easily. Eye droppers work well for moving the melted metal around. I’d recommend using a rimmed paper plate to contain the mess.
Try imprinting a Lego or toy car in play dough and pouring the molten gallium into the imprint. When it solidifies, you’ll have a cast of the item you imprinted! (It takes a while.) Gallium coats glass to create mirrored surfaces, so you can pour some into a small jar and use it to coat the sides. If you leave some in a puddle on the bottom of an upside-down jar, you can watch crystals form.
In other words, it’s pretty awesome!