I took some behind-the-scenes video when we were photographing my new book “STEAM Lab for Kids” last summer. Here’s a fun engineering project from the book! #summer #fun #balloon #rockets #STEAM #STEM
Footballs take crazy bounces, partly due to the occasional transformation of rotational (spinning) energy to linear kinetic (forward motion) energy when a football hits the ground. We used an experiment created by Kelly O’Shea to replicate this cool phenomenon! Try it to see for yourself how the second or third bounce can be higher than the first one! No wonder it’s so hard to catch a football!
For more Super Bowl physics fun, make paper footballs and have your own match during the big game. Here’s my ScholasticParents.com article on how to make them, how to play and the physics behind the fun! To see paper footballs in action and learn why players stay close to the ground when they tackle, check out this Super Bowl Science segment (above) I did this week on our Twin Cities CBS station.
And if you’re a Vikings fan like me…
Blowing bubbles is a fun way to experiment with surface tension.
Dish detergent lowers the surface tension of water which allows you to blow bubbles, and additives like glycerine, corn starch and baking soda make bubbles more elastic and resistant to popping. (More science below.)
- You can use a statically-charged balloon to make a bubble glide across glass as if by magic: (Instructions in video.)
2. Create a square bubble by making a cube from straws: (Submerge the cube in bubble soap made using the recipe below, pull it out, blow a bubble above it and let the bubble drop into the cube)
3. Or blow a bubble inside a bubble inside a bubble by coating a smooth surface like glass and using a straw dipped in bubble mix (recipe below) to blow bubbles inside bubbles:
Here’s our recipe (from Outdoor Science Lab for Kids- Quarry Books 2016) that can also be used to make giant bubbles:
-6 cups distilled or purified water
-1/2 cup cornstarch
-1 Tbs. baking powder
-1 Tbs. glycerin (Corn syrup may be substituted for glycerine.)
-1/2 cup blue Dawn or Joy dish detergent. (Fairy, Dreft or Yes work well in Europe.)
The Science Behind the Fun (from Outdoor Science Lab for Kids-Quarry Books 2016)
Water molecules like to stick together, and scientists call this attractive, elastic tendency “surface tension.” Surfactants like detergent molecules, on the other hand, have a hydrophobic (water-hating) end and a hydrophilic (water-loving) end. This makes them very good at reducing the surface tension of water.
When you add dish detergent to water, the lower surface tension allows you to blow a bubble by creating a thin film of water molecules sandwiched between two layers of soap molecules, all surrounding a large pocket of air.
Bubbles strive to be round. The air pressure in a closed bubble is slightly higher than the air pressure outside of it and the forces of surface tension rearrange their molecular structure to have the least amount of surface area possible. Of all three dimensional shapes, a sphere has the lowest surface area.
Of course, other forces, like your moving breath or a breeze can affect the shape of bubbles as well.
The thickness of the water/soap molecule is always changing slightly as the water layer evaporates and light waves hit the soap layers from many angles, causing them to bounce around and interfere with each other, giving the bubble a multitude of colors. Solutions like glycerine and corn syrup slow water layer evaporation, allowing bubbles to stick around longer.
Grab your coat and head outside to try this fun winter science project!
A large plastic zipper bag
Cotton kitchen twine
a toothpick or wooden skewer
a spray bottle
a squeeze bottle or syringe (optional, but helpful)
a very cold day (below 10 degrees F works best, but you can try it on any day when it’s below freezing)
Note: This experiment takes lots of playing around and results will vary depending on how cold it is outside. Remind your kids (and yourself) to be patient and try it on a colder day if it doesn’t work the first time around! If the bag leaks too quickly, try making one with smaller holes around the string.
What to do:
- Use a toothpick or skewer to poke 3 small holes in the bottom of a zipper plastic bag. Make one in the middle and one on each end.
- Cut three long (3 feet or so) pieces of kitchen twine and knot them at one end.
- Carefully thread the twine through the holes in the bag so that the knots are inside the bag to keep the strings from falling through. Try to keep the holes from getting too big, since the bag will be filled with water and you’ll want it to drip out very slowly around the string.
4. Attach two more pieces of twine to each top corner of the bag (above the zipper) to use for hanging the bag
5. Go outside and hang the bag from a low tree branch or railing.
6. Tie each of the three strings to something on the ground, like a rock, piece of wood, or the handle of an empty milk carton filled with water to weight it down. Arrange the objects so that the strings loosely radiate out at around a 45 degree angle. (See photo)
7. Add food coloring to some ice-cold water in a pitcher.
8. Fill the spray bottle with ice-cold water.
9. Add the cold colorful water to the zipper bag hanging outside. Zip the top of the back to slow the rate of leaking.
10. Immediately spray the strings with water to guide the leaking water down the strings.
10. Wait for the water on the strings to freeze. Use your syringe to add a little bit more water to the strings (same color) and wait for them to freeze again. Repeat until you have a nice layer of ice/icicles.
11. Refill the bag, using a different color of ice-cold water. Spray the strings lightly again. Repeat step 11.
12. Add layers of color to the icicles until you’re happy with the way they look!
The science behind the fun:
Icicles form when dripping water starts to freeze. Scientists have discovered that the tips of icicles are the coldest part, so that water moving down icicles freezes onto the ends, forming the long spikes you’ve seen if you live in a cold climate. When you add different colors of water to icicles in sequence, the color you add last will freeze onto the tip of the ice.
You’ll find more fun ice science experiments in my book “Outdoor Science Lab for Kids” and in my upcoming books “STEAM Lab for Kids” (Quarry Books April 2018) and “Star Wars Maker Lab” (DK- July 2018)
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!
It’s fun to make a rubber-band powered car from cardboard, straws, and wooden skewers!
-glue (a glue gun works best)
-a plastic straw
-a CD (or a compass)
-pipe cleaner (optional)
Hints: Parental supervision recommended for hot glue gun use.
Here’s what you’ll be building:
What to do:
- Wrap cardboard around a large spice bottle so you can see how it bends. Cut a piece of cardboard about 9 inches (22cm) long to wrap around the bottle. Trim off the excess cardboard and tape it to create a tube.
- Trace a CD or use a compass to make 8 circles that are around 4 and 1/2 inches (12 cm) in diameter. Use a ruler to make a square around each circle and then diagonal lines to mark the center of each circle. Cut them out and glue two circles together until you have four wheels. Use skewers to poke holes through the center of each wheel.
- Poke skewers through each end of the cardboard tube, about 1 and 1/2 inches (4 cm) from the end of each tube. Make sure that the skewers are parallel and that they line up when you look through the end of the tube.
- Use a screwdriver to make the holes larger.
- Cut 4 pieces off of a straw that are about 1/2 inch (1.5cm) long. Glue them to the outside of each hole in the tube. Use a skewer to help align them. The skewer should spin freely.
- One at a time, put wheels on the skewers and glue the OUTSIDE of the wheel to the skewer. Make sure that the wheels are parallel to the car, and to each other as they dry. Cut off excess skewer.
- Poke a skewer down the center of one end of the car, parallel to the wheels so that it’s sticking out about 1 inch (3 cm.) See image above.
- Decorate the car!
- Tie three thin rubber bands together and hook them over the skewer that’s sticking out. If you have a pipe cleaner or wire, hook it onto the other end of the rubber bands. Drop the rubber bands down through the center of the tube.
- Grab the rubber bands from the end opposite where they are attached to the car. Remove the pipe cleaner hook and wind them around the skewer to create tension in the rubber bands. Wind them until they’re tight.
- Set the car down and let the wheels start to spin to see what direction the car will go. When you’re ready, let go!
- Measure how far the car traveled.
Enrichment: How can you make the car go faster or farther. Try using different kinds and numbers of rubber bands. How could you redesign the car to make it work better?
The Science Behind the Fun:
In this experiment, you use your body’s energy to twist rubber bands around the wooden skewer axle of a cardboard car. The energy is stored as elastic energy in the tightly-stretched rubber bands. When you let the car go, the rubber bands apply enough force on the axle to turn the wheels on the car and elastic energy is transformed into the energy of motion, which is called kinetic energy.
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!
Here’s a fun optics experiment, based on one created in 1842 by Jean-Daniel Colladon, that you can do at home using a laser pointer and a bottle of water.
Parental supervision required. (Eye protection recommended for kids.) Never shine a laser pointer at or near eyes, as it can cause blindness.
Skullsinthestars.com has a well-written, detailed explanation of how light can be reflected in a transparent medium, like water.
This experiment is so awesome that our balloon-popping dog Heidi had to get in on the action! Try it, and you’ll see how much fun it is to play with the forces of physics using a blow drier and a ping pong ball or balloon.
Newton’s third law tells us that for every action, there is an equal and opposite reaction. As the air pushes up on the ball, the ball pushes back down on the air. Other forces are at work too, as pressure differences in the air column help the ball stay in the middle of the air flow.
It’s fun to track the weather, and you can create some cool meteorology instruments using stuff you have around the house. Here’s a great post by NOAA (The National Oceanic and Atmospheric Association) on how to make your own weather station.
It’s also fun and easy to do this cool convection current experiment, using warm and cold water to explore how air moves in Earth’s atmosphere.
To see how cold fronts move under warm fronts, you’ll need ice cube trays, water, blue and red food coloring and a clear container.
- Add water to an ice cube tray and add a few drops of blue food coloring to the water in each cube space. Freeze.
- Fill a clear container with room temperature water.
- Place one or two blue ice cube or two at one end of the container, and a few drops of red food coloring at the other end.
- Observe what happens.
The Science Behind the Fun:
Cold water(blue) is more dense than warm water and forces warmer water (red) to move up and over it.
This is similar to the way warm air is forced up when it collides with masses of cold air in the atmosphere. Warm air carries energy, and when there’s lots of moisture in the air, these collisions often result in thunderstorms.