What makes popcorn pop? If you have ever made popcorn you know that by putting hard,dry kernels of corn in a pan and heating them,the kernels will explode into popcorn Have you ever looked at the inside of the lid? (You have to use some sort of cover or the corn will pop all over the room.) After cooking popcorn you will always find water inside the lid. Where does it come from? The water came from the corn. There is a little bit of water in each "dry" kernel. When the corn is heated the water turns to steam. As it turns to steam it expands,pushing at the sides of the kernel. At last the kernel pops and the steam escapes. Since there is a lid on the pan, the steam is stopped by the lid. There it cools, condenses,and becomes water again.