They heated up so much that the pocorn kernels start to pop!!!
The microwave agitates the water inside of all of the corn kernels. The water turns to steam which expands and builds increasing pressure inside of the kernels until they pop (explode).
moisture which makes the kernels turn into popcorn
Popcorn kernels
You could try popping it. Usually you can tell very quickly, because if the kernels are too old, they won't pop very well. For microwave popcorn, the kernels will remain at the bottom of the bag. Popcorn has a shelf life of approximately two years. After this, it loses moisture and can become stale. It can also expire if the kernels are not stored properly. Popcorn dries out. The tiny bit of moisture inside the kernel is what causes it to pop. Without the moisture, the kernel remains.
Popcorn kernels pop when the water inside them expands, turns into steam and ... be too high for people at risk for heart disease, while added salt can lead to hypertension. ... Microwave Butter Popcorn & Lung Cancer Risk ...
Popcorn kernels have water inside. if the water dries out, it won't pop.
I understand that there are special sealed containers of popcorn suitable to cook in a microwave. Apparently, there are instructions on the label. The reason why special sealed containers are used is to prevent the popcorn shooting all over the inside of the microwave. One website stated that it was possible to microwave popcorn placed inside a brown paper bag!
If you are discussing popcorn kernels here (I wasnt sure) it is because they have moisture inside of them and when they are heated,moisture expands and they Pop.
All popcorn contain a small amount of water. When the popcorn gets heated the water inside the popcorn kernel turns to steam. The steam then starts to pressure the kernel shell and soon bursts making the kernel inside out, and the soft stuff inside the kernel puffs.
Popcorn pops in a microwave because there is a tiny amount of water trapped inside the kernels When that water is heated it turns to steam. Pressure builds and then the kernels pop!
The popcorn kernels all contain a drop of water that turns to steam when it is heated. The steam expands the kernel until it pops.
Believe it or not, most hard popcorn kernels have tiny bits of water inside. When these kernels are heated, the water gradually expands and turns into steam. At a certain point, the increasing steam can no longer be contained inside each kernel and explodes through the hard coating, causing a pop. The steam also cooks the starchy material inside kernels, turning it into the fluffy stuff we know as popcorn. Why don't some kernels pop? Such duds probably don't have enough water inside to pop them. From the Kid Wiki Answers