Candy that would pop or fizzle in your mouth have been around since the 1800’s. Scientists back then mixed together a sugar syrup (that contained very little water) with baking powder.
Baking powder is a mixture of a powdered acid and baking soda. When these two molecules are dry, they do not react at all. However, if they are dissolved in liquid they react rather well to form bubbles of carbon dioxide gas.
In these old candies, the liquid in your saliva provided plenty of fluid to dissolve the sugar and baking powder! This gave the candy a sour taste and a curiously foamy texture.
The next century found a new twist on this idea that is rooted in the four basic concepts of science:
In order to create what is now called Pop Rocks, scientists followed a simple procedure for creating hard candy. Of course, there was one small addition they made to the boiling syrup. Unlike older candies which relied on the ATOMS in the candy rearranging to form new gas molecules within your mouth, scientists pumped carbon dioxide gas DIRECTLY into the cooling hard candy.
These “exploding” candies provide an interesting sensation. Within their package, these candies look like large, ground-up crumbs of hard candy. However, once inside your mouth, these “crumbs” pop and fizzle. In fact, it is very easy to hear someone eating this candy from across the room!
HOW DOES IT WORK?
As the syrup is cooled, scientists need a way to keep the carbon dioxide INSIDE the candy. Under normal conditions, this gas would DIFFUSE out of the candy and back into the atmosphere.
So, scientists altered the environment of the cooling syrup by using air pressure to keep the carbon dioxide from escaping the syrup.
If you increase the air pressure surrounding the cooling syrup, it can lower the DIFFUSION of carbon dioxide into the environment. It’s almost like trying to stand up while someone is sitting on you. It would take a lot more effort!
As the candy hardens, pockets of carbon dioxide gas become trapped. And, since these pockets of gas were squeezed together because of the increased air pressure, each gas pocket has a higher DENSITY of ATOMS than is found in the atmosphere.
I’m not saying there are more ATOMS within the tiny gas pockets of these candies than in the ENTIRE atmosphere. But if you were to measure the size of this gas pocket and compare it to an equal of space within the atmosphere, the DENSITY of ATOMS within the candy would be much higher!
OPEN UP AND SAY AHHH…
Once the saliva in your mouth dissolves the candy, DIFFUSION causes the pressurized gas to escape rather quickly. And while this gas is escaping, you feel and hear these tiny explosions of carbon dioxide gas bursting through the candy.
Even through all of these tiny explosions, no ATOMS are being created or destroyed which is stated within the LAW OF CONSERVATION.
And don’t fall for the old myth that eating this candy and drinking soda pop will cause you to explode. I spent way too much time as a kid trying to see if this works (okay, I tried it again last week!)
Learn more about chemistry concepts (and many more) in the Classic Science: Series for the Family and be certain to come back every Thursday or subscribe to The Blog of Mr.Q to learn more about how to teach science during breakfast, lunch, and dinner!








