With the fall term gearing up, you've got precious little time left to hang out with your kids before they're trundled off to school. Entertain the ankle-biters and get their brains primed for learning with these amazing scientific food hacks.
Who needs a grill when you can cook a hot dog to perfection using only the power of electricity?
For this experiment, you'll need a fully-thawed (and precooked) hot dog, two nails, an old power cord that you're OK with never using again, and a nonreactive surface. Separate the power cord from whatever appliance it was attached to, and strip off the last inch of insulation from the ends of the cable (the opposite end from the plug).
Coil the wires around each nail and insert them into the hot dog, which should be sitting on the plate a safe distance from things that could potentially catch fire. Plug in the power cord and watch the hot dog cook without any apparent heat source. Once the dog is done, unplug the cord (before touching anything else), carefully remove the red-hot nails, and enjoy your piping-hot dog.
This is a perfect example of Joule heating, wherein electrical energy is converted into heat energy as it passes through a resistor. Electric space heaters operate on the same principle. In this case, the hot dog acts as the resister of the circuit, since electrons flow through the metal wires far more easily than they do processed meat sticks, and accumulates the resulting heat energy.
In the dog days of summer, nothing helps beat the heat like an ice-cold slushie. But rather than trek through the unbearable temperatures to your nearest 7-11, just shake up a bottle of soda and put it on ice for a bit.
Turn a seemingly normal frosty bottle of soda into a mountain of frozen Coke slushie. As the video explains, you first must give the bottle a good shake, then freeze it for just over three hours. When you pull it out of the freezer, loosen the cap slightly, invert the bottle and pour out an aerated, frozen, treat.
This trick is accomplished via supercooling—that's when a liquid is cooled beyond its regular freezing point without crystallizing into a solid. Typically, when water gets cold enough (0 degrees C) ice crystals will spontaneously form around microscopic impurities within the liquid, causing the water to ice over. To super-cool it, you'd normally have to eliminate all these impurities using reverse-osmosis or similar such purification technique. However, the carbonated pressure within a bottle of coke can prevent the crystallization process so long as it is maintained.
By shaking the bottle before you freeze it, you distribute the carbonation evenly throughout the liquid (not just packed into the empty space at the top of the bottle). This increased pressure in the liquid prevents it from crystallizing during the cooling process, but once you break the cap's seal, the pressures in and outside the bottle equalize, causing the carbonation to escape from the soda as it exist the bottle, resulting in a frothy, aerated slush.
Crystallization isn't all bad, and in some cases, can be rather delicious. Teach your kids about solutions and precipitates with this classic experiment.
Grow candied crystals from a pot of seemingly clear water. You'll need:
- a saucepan
- 3 cups of water
- enough water to fully dissolve the sugar
- a few lengths of string (each about 4" long)
- a glass bowl or cup
- a chopstick
Heat the water and sugar in a saucepan until the sugar completely dissolves and the mixture turns clear. While that's heating, soak the strings in a bowl of water for 5 minutes, then squeeze out the excess liquid.
Roll the string in sugar to coat, then tie one end to the middle of the chopstick (this will act to keep one end of the string out of the sugar solution). Pour the hot sugar water from the saucepan into the glass bowl, set the chopstick across the mouth of the container, letting the strings hang down into the solution. Let them sit for about a week before removing the strings, which should now be covered in a thick layer of crystallized sugar.
This is the opposite effect seen in the super-cooling experiment above—instead of preventing crystal nucleation from occurring, this actively promotes it—much like modern cloud seeding programs. As the sugar dissolves into the water, it forms a solution—a homogeneous mixture of a solute and solvent, typically in the liquid state. To extract that sugar back out of the water, it must undergo precipitation. And to do so, the dissolved sugar molecules need something to stick to in order to get the process going. That's where the sugar-coated string comes in. By coating the strings in sugar crystals, you provide the dissolved solids a "seed" to form around.
Out of butter again? So what the heck are we supposed to put on our toast? Not to worry, with a mason jar and a little elbow grease, you can churn up some fresh butter in under five minutes while illustrating to process of aeration.
Half-fill a half-pint mason jar with heavy cream, add a dash of salt, and screw on the cap. Shake the jar for a good minute or two, then pop off the cap, and check the consistency of the proto-butter (it should be roughly whipped cream at this point). Put the top back on, give it another minute of shaking and recheck. Continue this until you reach the necessary texture—or your arms fall off, whichever occurs first.
Butter is essentially aerated milk fat. The forceful shaking action first breaks down the lipid coats of the individual fat molecules. Once open, these fat molecules can link together into longer clumps and chains. These lumps tend to congregate around gas molecules, trapping them in a loose network of milk fat (really more of a froth or foam). As the clumps of butter continue to group together into larger and denser portions, the air has fewer places to be trapped. These bubbles eventually pop and leak out of the concoction as buttermilk.
The butter and buttermilk are then separated. The buttermilk is bottled and sold while the butter itself is kneaded into its normal consistency. Interestingly, butter isn't a solid; it's a water-in-fat emulsion. The water droplets are so finely dispersed through the lipids, it appears dry.
These simple demonstrations will help whet your kids' appetites and, hopefully, their thirst for knowledge as well. If you know of any other suitable culinary experiments, let us know in the discussion below! [Science Buddies - Food Republic - YouTube - Top Image: Kirill__M, Hot Dog: oskay / Flickr, Rock Candy: PhotoSGH]