Posts Tagged With: friction

Program 44: Playing with our Food…

Okay. Sometimes, my G3 programs come together in very interesting ways. My idea for this program started with a beautiful banana. As some of you may recall, I’m a big banana fan – they are just so darn interesting! And then it grew from there. There are so many fun science projects and demonstrations you can do with food that I just couldn’t help myself. So for our first G3 program this Fall, I had our G3 scientists take on the following:

  1. We investigated to see if TOTAL brand cereal uses real iron in its cereal flakes. [“Eating Nails for Breakfast”]
  2. For fun, I challenged the scientists to pull a table cloth out from under a full table setting…and explain to me the science behind the results [“Tablecloth Trick”]
  3. I had the scientists work hard for their afternoon snack by making their own butter.
  4. I demonstrated how the magical banana can actually form the base for a very delicious “ice cream” treat.
  5. Finally, I let our scientists combine their love of science with their creative sides by tattooing bananas with fun images and talking about how the heck that’s even possible!

EXPERIMENT #1:  “Eating Nails for Breakfast” [from Steve Spangler]


  • TOTAL brand cereal [enough so that each scientist can have a sandwich bag filled about 1/3 of the way up – for my group of 22 or so scientists, I used 1-2 full-sized boxes of cereal. I chose to pre-fill baggies with the cereal]
  • Water for each scientist [I just distributed a standard water bottle to each scientist, though they only used a small portion of the bottle]
  • Sandwich bags that zip closed [2 per scientist]
  • Strong magnets [I actually own a nice neodymium magnet that I picked up from the Steve Spangler store…and that worked best for us as a group. But I have seen the experiment work with bar magnets, and according to its packaging, my cow magnet should also have worked well. If you have enough magnets to distribute around, all the better. I passed my one neodymium magnet around from table to table…]

The trick with this experiment is that it actually takes some time to complete it and get to the results phase. So I started our program hour with Part One of this project, and we returned to it before the scientists had to go home at the end of the program hour.

home_box_newAfter explaining to the group that we were going to try and verify that Total cereal adds actual iron to its cereal flakes, I distributed the pre-filled baggies of Total cereal to each scientist and asked them to seal up the bag (getting as much air out of the bag as possible) and smash the cereal into small pieces/crumbs. As you can imagine, my crew had a LOT of fun pounding their cereal into smithereens. After a few minutes, I asked each scientist to pour their cereal crumbs into a second, empty baggie and then fill the bag about 1/3-1/2 up with water. [I discovered during my own early testing that the process of crushing the cereal flakes created some small holes/tears in the original baggie…which of course made for quite a mess when I added water to the bag. My simple solution was to have every scientist start with a fresh bag before we added the water.] Once the water was added, it was time to set this project aside for at least 30 minutes. Truthfully, you might have luck returning sooner than that, but it’s better to be safe than sorry!

nails_breakfastWhen we came back to this experiment at the end of the hour, the next steps were very simple in deed. I asked each scientist to shake their bag of water-logged cereal flakes…which essentially breaks up the flakes even further so you get something that looks rather like a cereal slurry. If any of the scientists seemed to have a little too much air in their bag, I helped them to carefully get some of that extra air out and then reseal the bag. Each scientist then laid their bag of slurry flat on the table surface and everyone took turns pressing the neodymium magnet directly onto their bag. When you do that, the magnet pulls literal iron filings up from the slurry to the surface of the bag. You can even drag them around the top of the bag with the magnet’s help! Our scientists (and their parents!) were amazed to find actual iron in a breakfast cereal!

In the video below, Steve Spangler does a great job of explaining the experiment itself. In the 2015 National Geographic Kids book, Edible Science, there’s also a wonderful description of the same experiment (pg. 18) along with an explanation for why the heck manufacturers put iron in our cereal:

Iron is naturally found in meat and some vegetables. In those foods, the iron exists as one part of a large molecule, such as hemoglobin. However, the easiest way for a food manufacturer to increase the iron content of a product is to add pure, metallic iron. Many cereal makers grind iron into metal dust and mix it into the batter for their flakes… (pg. 18)

DEMONSTRATION #1: “The Tablecloth Trick[From Steve Spangler]


  • I used an actual Tablecloth Trick demonstration pack from Steve Spangler that included the special tablecloth and a full table setting (plastic plate, plastic bowl, plastic cup, fork, knife, and spoon)

table-experimentHonestly, I did this demonstration because I knew the kids would have fun with this challenge. This was one of my take-homes from my Steve Spangler conference in July 🙂 I simply challenged my scientists to pull the tablecloth out from under the full table setting. I demonstrated first, and then without giving any tips or instructions, I asked the scientists to line up next to the table where I had set up the tablecloth and give it their best shots…with a promise that we would talk about the “science” behind the demonstration after they had all had a turn.

If you go to the first link above, Steve Spangler’s web site does a great job explaining how to best set up the demonstration…and what the science behind the trick actually is. Basically, you need to:

  • Spread the tablecloth out onto a flat tabletop with about 2 feet of the tablecloth on the table. Make sure there are no wrinkles.
  • Place the cups, plates and utensils on top of the tablecloth relatively close to the edge of the cloth (increases the chance of success for beginners).
  • The trick is to grab the ends of the tablecloth with both hands and quickly pull the cloth straight down and away from the table. The key is the quick, downward motion – almost like you’re whipping or yanking the cloth away. Keep saying to yourself, “Pull down… not out.” Make sure to pull perpendicular to the table and not at an inclined angle.

Amazingly, I think all but 1 of my 22 scientists were able to successfully do this trick in the first go! What is the science involved in this trick? Inertia and Friction. According to Sir Isaac Newton’s Law of Motion: 1) an object will remain at rest until a force acts on it, and 2) an object in motion will remain in motion unless a force acts on it. Thus, our full table setting (plates and silverware) will remain in place (at rest) unless a significant force acts on them. Where does the Friction come into play? Well, initially, all of the objects (the plate, bowl, cup, utensils) are at rest (not moving). When you pull the cloth, friction acts on the objects in the direction of the pull for a short time. But the tablecloth (with no hem or edging) is slippery, so these forces are small and the cloth sneaks out from underneath the objects.

EXPERIMENT #2: Snack Time…Let’s Make Butter!


  • Heavy whipping cream (room temperature – out of the fridge for 6-8 hours)
  • Small containers with secure lids (In the past I used recycled 4 oz. baby food jars, one for each scientist. This time I used small mini cups…and they worked SO much better!)
  • A little salt for flavoring
  • Bread, for snacking
  • Plates to put the snack on 🙂

Even having done this before with a different group of scientists, I’m still amazed at how easy this is…and how satisfying. There’s something really nifty about letting my scientists make something that they can instantly use (or consume). I passed out the mini cups, which had about 1/4 to 1/2 inch of heavy cream in the bottom. [This small amount of cream produces plenty of butter for each individual scientist, approximately 1-2 servings.] I instructed my scientists to add a pinch of salt for flavoring if they wanted (most of us eat salted butter at the dinner table). We sealed the cups tight, and then it was just a question of some time and arm muscle. You need to shake the cream in the container for about 10 minutes to instigate the physical change in the cream. Basically, when you agitate the cream for a long enough period of time, you are helping to separate the fat solids from the “butter milk.” [NOTE: Leaving the cream at room temperature for a while helps the physical transformation along at a quicker rate.] Every one of the scientists saw the full physical change and achieved both the full butter solids and the butter milk! And everyone loved the flavor of their butter on the bread I passed out to all 🙂

DEMONSTRATION #2:  Banana “Ice Cream”

Pages-from-Nom-Nom-Paleo-50-Page-Preview-51-785x1024While my scientists munched away on their bread and butter, this seemed like the perfect time to give them a little something sweet to sample at the end of our snacking. I recently discovered – while browsing through my Nam Nam Paleo cookbook, that you can make the most amazing fake ice cream using frozen bananas as your base.


  • 3 bananas (halved, placed in freezer bags, and frozen overnight)
  • 1 cup of frozen strawberries (you could probably use any frozen fruit here)
  • 1/2 cup of coconut cream (you can find that in most food stores in the aisle where they sell the fixings for adult cocktails)
  • 1 tsp. vanilla extract
  • A nice food processor

I carted my food processor in from home, and then proceeded to demonstrate to my scientists how to put together this recipe. After just a few minutes in the food processor, the ingredients really do have the texture and temperature of a nice soft-serve ice cream without using any milk or cream! The hero in this recipe is the banana. Bananas have high levels of pectins (a type of water-soluble fiber). To be frank, I don’t even understand the full “how does it really work” with this recipe. But there’s something that happens when you freeze the bananas and break up that fiber in the food processor that makes for fake ice cream magic (yum!). I had the scientists line up, and I gave them all a sample in a mini cup (like the ones we used to make butter). All of my scientists loved this recipe so much they came back for seconds…and all of the moms present seemed very interested in jotting down the recipe 🙂

ART/SCIENCE PROJECT:  Tattooing Bananas


  • 1 banana per scientist
  • Fun images for the scientists to use as templates
  • Scotch tape
  • Push pins or toothpicks (I found that push pins worked easiest, but I know some folks would prefer toothpicks if they plan on eating the bananas later)

Olaf_from_Disney's_Frozen 254-batman-logoenhancedThis banana project was literally the starting point for this entire ‘fun with food’ program. I was DYING to try this out with some of my regulars at the library. So easy, and such a quick reward for your efforts. This one did take a little pre-work on my end, though. I selected some fun images that I thought the scientists would have fun working with: Beeker, a Minion, Olaf, a Lego Ninjago, the Batman symbol, etc. I then measured my typical banana and created a rough outline in a blank PowerPoint document (about 2 inches by 7 inches) and then sized the images to be approximately that size. [I wanted to ensure that the images I passed out to the scientists would roughly fit along one side of their bananas, and wouldn’t be too large or too small.]

After distributing the bananas, I instructed the scientists to cut out the image of their choice. No need for precision here – you want there to be a wide border around the image itself. I then had them tape the image in place on their banana. And then it’s just a question of a little time and patience. You use the push pin to punch holes around the ouline/lines of the image (like tracing the image with a series of dots). When you think you’ve put holes in all of the major lines, you can remove the paper and then just fill in some of the lines with more dots to make for more solid lines (think of it like connecting-the-dots).

Minion Banana

Minion Banana

LEGO Ninjago Banana

LEGO Ninjago Banana

Almost instantly, the dots create a brown discoloration on the surface of the banana. This happens because of oxidation. Bananas contain polyphenol oxidase and other iron-containing chemicals which react with the oxygen in the air when the cells are cut open (similar to what happens when rust forms on a piece of metal). We had some pretty terrific art come out of this science demonstration/project, and as a bonus, the scientists could take the bananas home and eat them later! The push pins actually don’t push very far beyond the skin of the banana, so 1) the bananas stay fresh for a while, and 2) the artwork on the skin remains just as lovely a day two after you complete it.


As you can see, we had a lot on our ‘plates’ for this first program (ha ha), but it was tons of fun for all! Who doesn’t love playing with their food, right?… 🙂


Categories: Food Science | Tags: , , , , , , , | Leave a comment

Program 29: Balloon Bananza!

I felt it was time for our G3 scientists to once again have some fun with balloons. Not only are balloons a pile of fun, but they help us learn a lot about science! In fact, in just this one program our G3 scientists learned a little about:

  1. The Properties of Polymers
  2. Centripetal Force
  3. Friction
  4. Newton’s 3rd Law of Motion

We started the program with a quick discussion about the properties of polymers. In particular, how the rubber in balloons is made of long strands of molecules called polymers. And it is the elastic quality of the polymers that allows the balloon rubber to stretch. Our conversation then turned to centripetal force and friction. The word “centripetal” is actually Latin for “center seeking.” And that truly describes this force. Without centripetal force, objects would not be able to travel in a circular path (they would only be able to travel in a straight path). One example is how a satellite orbits the earth. In this case, the centripetal force is supplied by earth’s gravity (think of it like an invisible thread that links the earth to the satellite and keeps the satellite moving around the earth in a circular orbit). Another example is the swings ride at an amusement park, where the centripetal force is supplied by the chains that link the chairs to the central pole. I shared my favorite video with the groups. In the following video, Jeff Williams on the International Space Station (ISS), shows that, due to centripetal force, the bubbles in his iced tea package move to the center of the package and form a large, singular air bubble when the package is put into a circular path.

EXPERIMENT #1:  The Balloon Skewer, or what I call, “Balloon on a Stick”


  • Clear balloons are a must (a bought a package of 70+ at a party store)
  • Wooden skewers (the longer the better – again I found some at a party store, but I suspect some grocery stores have them as well)
  • Some liquid vegetable oil in a cup

This is definitely an experiment designed to impress a crowded room 🙂 Thanks to my favorite scientist Steve Spangler, I impressed our scientists with a demonstration from his web site called The Balloon Skewer. By coating a standard bamboo skewer with vegetable oil (for lubricant), you can push the skewer in one side of the balloon and out the other side…without popping it!  [The trick is making sure the entry/exit points are where the balloon’s rubber is LEAST stressed, or more opaque looking then the rest of the balloon – near the base where you tied off the balloon, and at the opposite end and top point of the balloon.]  Each G3 scientist was given a clear balloon and a skewer to try their hands at this demonstration. An important early step is inflate the balloon as large as you dare, and then release 1/3-1/2 of the air before you tie off the balloon. This actually helps stretch out the polymers and gives you a better chance at success when you aim to slip the wooden skewer between the polymer chains and through the balloon itself. The vast majority of our scientists were a success…though the sounds of popping balloons could be heard here and there throughout the room.  Practice makes perfect!

Experiment #2:  The Spinning Penny


  • Clear balloons are a must
  • One penny per person

With our next experiment, we had a chance to see centripetal motion at its best. The Spinning Penny is an experiment described on the Steve Spangler’s web site. The experiment itself is very simple. A single penny is placed inside a clear balloon. The balloon is inflated and tied off with the penny still inside.  After shaking the penny a bit, the balloon is then swirled to help start the penny on a circular path inside the balloon itself. Due to the limited amount of friction, the penny can stay on its circular path for close to 30 seconds before gravity begins to slow it’s path! Our scientists all managed to create this very cool demonstration of centripetal force. [Special Note:  It is important that the balloon is pointing toward the floor as well as your eyes when you inflate it – there is a danger of a choking hazard if you choose to tip the balloon above our head to inflate with the penny inside!]

Experiment #3:  The Screaming Balloon


  • Clear balloons are a must
  • One zinc hex nut per person (though any size works fine, we used a 1/4 inch diameter nut)

This experiment is actually a fun variation to The Spinning Penny. For The Screaming Balloon, we replaced the penny with a zinc hex nut…and guess what? The nut also moves on a circular path within the balloon due to the centripetal force we supply, but there is more friction between the hex nut and the balloon thanks to the the shape of the nut, and thus we get a high-pitched whining sound! Very fun for us…maybe not so fun for friends and family 🙂

Experiment #4:  Balloon Rockets


  • Any balloons will do (we made sure everyone used the same size balloon for fairness since we did some mini races)
  • String
  • Straws (if you have the bendy kind, you can just cut off the bendy portion)
  • Tape (any kind will do, though masking tape proved a little easier to work with)
  • Chairs

What better way to see Newton’s 3rd Law of Motion in action than some friendly competition with balloon rockets! According to Sir Isaac Newton and his 3rd Law of Motion,

For every action, there is an equal and opposite reaction

To test this principle, we followed the guidelines of Science Bob to create our very own balloon rockets. We divided our group of scientists into 2 teams, and each team assembled a rocket “track” – a pair of chairs with some kite string strung between them (like a zip line). A straw was threaded onto each string. Each scientist received a colored balloon (clear is not necessary for this experiment), and was instructed to inflate the balloon as large as they wanted without tying it off. While pinching the open end of the balloon closed, the balloon is held under the straw and taped to it (with the mouth of the balloon pointing in the opposite direction that you want the balloon to travel in). When you’re ready to the see the balloon in action, you just unpinch the mouth of the balloon and let go! The result mimics the take-off of a rocket, with the air pushing back in one direction and propelling the balloon in the opposite direction. We had some friendly competition to see which team’s balloon would travel the farthest. Every scientists received a small prize for their efforts 🙂

At the end of our hour, every scientist was able to bring a copy of these simple demonstrations and experiments home with them.  Below is a nifty video showing our scientists’ efforts during all of the balloon experiments. Until next time!…

Categories: Forces, Motion, Polymers | Tags: , , , , , , , | Leave a comment

G3 Program 17: Marble Runs!

Our G3 scientists had a lot of fun with this program. “Marble Runs” tested the best of their creativity and ingenuity…but what exactly is a marble run and how can you create one? Well, marble runs come in all shapes and sizes. Some run only along walls, and others swirl around entire rooms. Trying to figure out how to get one started? One really great resource “The Tinkering Studio” blog hosted on the Exploratorium web site. They have a great article dedicated to “marble machines.”

Toothpick run of San Francisco Bay Area

To get us in the right frame of mind, we watched a video about Scott Weaver – he spent the last 35 years creating a model of the San Francisco Bay Area from 100,000+ toothpicks! His run is free-standing and actually uses ping ping balls for its course. We also saw a Japanese cell phone commercial that utilizes a long run through a forest, where the wood steps are actually tuned to different musical notes! (As the ball moves down the track, it plays – I think –  “Ode to Joy”).

The possibilities are endless!

Our G3 marble runs required a lot of creative thinking from the G3 crew. I supplied several tables filled with every kind if material or recycled item that a person could want – and then I let the scientists have their pick of materials to create their runs on peg boards. There were no rules or restrictions – whatever they wanted to use, they could. Some worked in teams, some chose to work alone. Some created fairly traditional marble runs that zig-zagged from side to side on the peg board descent, while other scientists threw in a few extra “tricks” here and there. Check out the really cool results below from our G3 Marble Run playlist on youtube!


Categories: Design, Motion | Tags: , , , | Leave a comment

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