 
Candy poppers are crystals of candy which pop and crackle when you put them in your mouth. There are many varieties and brand names, but they all do the same thing. The effect is quite powerful ... if you open your mouth while they're crackling, the noise is easily audible to others.What's going on with these candies? Why do they crackle? What causes the effect? On this page we'll answer all these questions, and others too! 
We used two packages, one of pink and one of green crystals. You can see in the picture at the left how much candy you get in a package of 'Poppers'. The crystals come in all sizes, from tiny ones that resemble powder to much larger ones like the one shown at the right. What makes them pop? The answer is really simple; each crystal has bubbles of CO2 embedded in it. When the candy gets wet, it starts to dissolve, and the carbon dioxide gas is released. It pushes its way out of the thin layer of candy remaining, causing a popping noise. 
We simulated this by adding a small amount of water to some crystals.If the crystals become surrounded by water, as in the picture at the right, you can't hear the popping, but you can clearly see the carbon dioxide gas bubbling out of the crystals. (This is difficult to see in the photo, so we highlighted the bubbles with arrows). 
To observe the popping effect, we added a small amount of water to a big pile of crystals.
This allowed some of the crystals to dissolve without getting surrounded by water, so we could hear the crackling. The noise was easily audible.This method also produced another effect which was quite noticable. Many of the crystals began jumping around; we tried to simulate this in the animation at the left. Look closely. What supplies the force that causes these particles to move? The answer is that the escaping carbon dioxide supplies a force to a piece of crystal just like exhaust gases from a rocket supply a force to lift it. This is an illustration of Newton's first law. 
There is a considerable amount of carbon dioxide released from the crystals. You can see this clearly in the photo at the right, where a spoonful of crystals was immersed in a beaker of water. Collecting the gas and testing it (by seeing if it will cause a burning piece of wood to extinguish, for example) would be quite easy. The question that now immediately comes to mind is whether enough of the gas can be collected to actually make use of. That's what we tried to do next. 
We used a very small balloon, which we planned to fill with crystals before adding some water. The small size of the balloon made it quite difficult to get the crystals inside, but we managed to load a full package. Adding an eyedropper full of water to the balloon caused the crystals to begin to dissolve; as we sealed the top, the balloon clearly began to expand as the amount of carbon dioxide in the air inside the balloon increased. Although we made no attempt to release and store the gas, it would be quite easy to do. We hope this demonstration gives you some ideas about how you might use the candy to generate carbon dioxide, and what you might do with it. I once emptied about ten packages of the crystals into our cats' litter box after refilling it with clean litter. It made a nice pile at the back, which the cats ignored. Until one of them managed to pee on the pile of crystals. From the speed with which she exited the box, I assumed that she was rather upset. |