Why is this the answer?

The answer is popcorn because this riddle describes the amazing and fun way a tiny, hard corn kernel changes into a light, fluffy snack. It is a fantastic secret hidden inside a small seed, and the riddle uses clever language to describe the cooking process. Let us look closely at the first line of the riddle: "What makes a loud noise when changing its jacket." Before we cook it, popcorn is a hard, little seed called a kernel. This kernel has a tough outer shell, which is exactly like its "jacket." Inside every kernel is a tiny drop of water. When you put the kernels in a hot popper, that little bit of water turns into steam. The steam is trapped and gets very, very hot, building up a huge amount of pressure inside the kernel. Suddenly, the pressure becomes too powerful for the hard "jacket" to hold, and POP! The shell breaks open with a loud noise. The jacket changes because the shell has cracked, and the inside has puffed out. That loud pop is the sound of the kernel exploding from the heat. Next, the riddle mentions that it "becomes larger." Think about how small a hard kernel is. When it pops, the inside explodes into a big, white, fluffy piece of deliciousness. The popcorn expands greatly in size. It goes from being a tiny seed to a much larger, airy treat. This huge change in size is what makes it such a great snack. Finally, the riddle says it "weighs less." This is a clever word trick. A piece of popped popcorn does not actually lose any weight, but it feels so much lighter to you. Before it pops, all the material is packed tightly into a small, dense kernel, which feels heavy. After it pops, it is mostly air inside that big, fluffy cloud of corn. Because it is so airy and not dense anymore, when you pick up a giant bowl of popped popcorn, it feels light as a feather. The big volume and the light feel make the riddle perfect for popcorn.