how is chemical burning similar to a nuclear chain reaction?

Answer 1

You try to light a fire in the fireplace or you try to light charcoal briquettes in the barbeque. You have to assemble a critical mass of briquettes or logs. Then you have to squirt lighter fluid or rolled newspapers. Finally (Gott sei dank!) something catches, the one fragment heats the other fragment, and finally you have a fire that you can keep going on and on as long as you have logs or briquettes.