"Ken let out a painful cry when the cooker fell down on his toes."
Can I substitue the word "when" for "while?"
No, because when emphasized the exact moment. It fell. It hit his toes. He screamed. It all happened at once.
While suggests a long duration. Perhaps Ken would moan while water dripped on his toes, but not when the cooker fell.
And you don't need the down in there. Things generally tend to fall in that direction.
Last edited by Rover_KE; 21-Aug-2014 at 08:13.