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Apr. 22, 2011

Science Dad on What to Do With All That Candy!

by Vince Harriman

Click to enlarge images
Back when I was a kid and we walked for miles uphill in snow to school and back, holidays were not quite the avalanche of candy that they are today. Now I'm not complaining -- I love candy as much as the next kid -- but we really do seem to be buried in candy several times a year. This year I decided to put some of it to good use and see what kind of science we can pull out of a basket of candy!
 
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Calculating the speed of Peeps, um light
 
We'll start by recycling an experiment we did a month ago: measure the speed of light. We have a variety of colorful bunny peeps this year, which are better than the chicks. You can see that straight out of the box they are flat, tightly packed, and ready to be nuked in the name of science. Microwave the peeps on low for 60 seconds or so, watching them carefully. When you see the peeps start to swell, pull them out. You'll notice the pan now has a bunch of hot spots surrounded by uncooked peeps. The microwave generator inside the microwave sends out a very regular pattern of waves — and these waves have high points (nodes) and low points (anti-nodes) just like the waves you see at the beach. The high points (nodes) represent the high point of energy while the low points indicate low energy.
By measuring the distance between points we could find the wavelength — 4 5/8 inches, which we converted to the metric system and got .11178 meters. Speed (velocity in this equation) is easy to calculate: V=(wavelength)x(frequency). To find the frequency, all we had to do was open the door of the microwave — the frequency is listed on the safety panel: 2450 megahertz. A hertz (the word hertz is used for both singular and plural) means one cycle per second. A megahertz is a million cycles per second. So: V (speed) = (0.11783 meters) x (2450 x 1,000,000)=288,694,267 meters/second.
 
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Brownian motion and Brown M&Ms
 
Next we decided to 'see' the motion of atoms by witnessing Brownian motion. I had Beckett and his friend and neighbor Charlie place M&Ms in three small containers, then we simultaneously filled each container with water: one with ice water, one with room temperature water, and one with near boiling water. (Parents please note-the boys poured the cold water, I poured the hot water!) We labeled the containers and observed the changes carefully. The candy in the hot water began to change immediately, while the candy in ice water changed the slowest. Charlie and Beckett both correctly identified the energy in the water as the force that removed the candy coating. The water molecules are constantly in motion, bouncing off each other constantly and bouncing into the M&Ms. The hotter the water, the more the water molecules are moving. And, as they move, the water molecules bounce 'candy' molecules off the candy.
 
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Brownian motion and water currents
 
Sticking with Brownian motion, Beckett and Charlie filled a baking pan with room temperature water and carefully dropped M&Ms in all six colors into the pan along one edge. They then placed a bag full of ice cubes and water right next to them. As in the first Brownian motion experiment, the room temperature water slowly started taking the color shell off the candy. This time, though, something different happened -- the dye started flowing away from the cold water. What is happening here is complicated. Everybody knows that water expands when frozen, unlike almost everything else in the universe which contracts when it gets colder. But water's dynamic and kinematic viscosity (viscosity means how thick the water is) also changes relative to its temperature -- which means that water flows at different rates at different temperatures. Very viscous liquids like syrup flow slowly. Liquids lacking in viscosity like rubbing alcohol flow very easily. In our experiment, adding a source of cold to an otherwise motionless body of water added a dynamic force -- as the water changed temperature, it changed how it flowed and moved, and this change in flow pushed the dye away from the cold source.
 
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Newton's Cradle
 
We were making a dent in our basket of candy, but there was plenty more. Moving away from atomic level science, we decided to learn about classical mechanics and build a Newton's Cradle. The Newton's Cradle (also called the executive clicker and Newton's pendulum) is perfect for demonstrating the Law of Conservation of Energy and Momentum written by Sir Isaac Newton. We built a small sturdy frame out of the wood left over from last week's work experiment, then drilled into some jawbreakers. We took a needle and dental floss (or you can use a very sturdy thread) and threaded the jawbreakers. Finally we measured and marked the diameter of the jawbreakers on the wooden support. Do this step carefully -- you'll want the jawbreakers just touching each other as they hang. We used thumbtacks to secure the dental floss to the support, hanging all of one side first, then turning the whole thing over and making sure that each jawbreaker was at the same level. We stood it up and started clicking and clacking. Pull one jawbreaker back and let it hit the ball adjacent to it. The ball will hit, transfer its energy to next ball, which will transfer its energy to the next ball, which will transfer its energy to the next ball, which will fly up taking most of the energy of the first ball with it. Now go eat an apple!
 
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Statistical Analysis of Color Distribution in M &M Candies
 
Next, I had Beckett just take a look at a bag of candy. We poured it out and arranged it by color. While this is more about math than science, it is a good way to have kids start thinking about the world in a 'math' way. Notice the distribution of colors is not uniform: 10 red, 8 brown, 12 yellow, 16 green, 12 orange, and 13 blue. While the factory workers don't care how many of a given color are in any particular bag, they do aim to have roughly equal numbers of each color in a bag (though there may be a marketing plan behind all the green ones.) Why are there different numbers of each color? Try this with any loose candy -- jelly beans, Skittles, Starburst, Spree. The more candy you collect, the more the numbers will approach each other.
 
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How many candies are in this cup?
Finally, we'll end with a classic. When I was a kid it seemed like every year someone had a 'guess how many of these things' are in this jar or container. Jelly beans in a jar, watermelons in a truck, pennies in a piggy bank. While this is a math problem, it has great value to many different branches of science. So, how many M&M candies are there in my 1/3 cup? You can figure it out several different ways. First, you could measure as accurately as possible a single candy to find its volume, then divide the volume of the 1/3 cup by the volume of a single candy. You could count the candies, individually, one by one. You could weigh one and figure out how much a certain volume weighs then work backwards. I will mail a king size pack of M&Ms to the first person to guess how many candies are in the picture to the left and leave a comment below!
 
If you still have candy left after all this, well, give me a call. I'll be glad to help you out!
About Vince Harriman

Science Dad, AKA Vince Harriman, is a freelance writer living in Annapolis. His two sons, Beckett-6 and Rowan-2 1/2 ask him 'why' approximately 6,542 times a day.

The views expressed are those of the author and are not necessarily those of Science Friday.

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