Pop Rocks pop because they contain tiny, high-pressure carbon dioxide gas bubbles trapped inside the candy. During the manufacturing process, molten sugar syrup is mixed with carbon dioxide gas under high pressure (around 600 psi), which forms these gas bubbles within the candy as it cools and hardens. When the candy dissolves on the tongue, saliva melts the sugar and releases the trapped gas bubbles. The sudden release of this high-pressure gas creates the popping and crackling sensation experienced in the mouth. This popping effect is a physical reaction caused by the pressure of the gas escaping, not a chemical reaction. The gas bubbles burst as the pressure inside them equalizes with the outside environment, producing the characteristic popping sound and sensation.