why does popcorn seem to pop at a somewhat consistent rate regardless of the amount, instead of all of them popping closer to at the same time?
In: Physics
Consider a pot with a layer of oil and popcorn on the bottom. When you apply heat, it goes into the oil which heats the kernels. Since the oil distributes the heat fairly evenly, all the kernels are being equally heated. However, things change dramatically when a kernel that’s just a little hotter than its neighbor explodes.
When a kernel explodes, it does so because the water inside is expanding to steam. That takes heat out of the local region, that is, the exploding kernel cools the surrounding kernels.
The heat required to vaporize water is about 540 calories/gram of water. That heat comes from the surrounding oil and kernels. But there’s a lot of oil and popcorn so a kernel elsewhere in the pot isn’t affected by the explosion as much as the immediate neighbors so it pops as well. So now you have two cooled spots, the first warmer than the second because the heat is still being applied. The next hottest spot pops a kernel and cools and the cycle continues until all the kernels have vaporized the water inside of them.
So basically what’s happening is the pot is alternating between heating and cooling regions of the pot.
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