Minecraft wouldn't save wordls unless you edit the chunks

What I expected to happen was...:
The worlds that weren't edited enough, it didn't save the world when you exit the app

What actually happened was..:
When I loaded a new world,after blowing up ice,the world was saved,but when I broke a block,it didn't save
Steps to Reproduce:
1. Generate a new world
2. Break a block
3. Exit the gane