Another factor in scientific discovery is chance ,or serendipity.many discoveries have been made by accident.for example,in 1839,the American inventor Charles Goodyear was searching fora treatment for natural rubber that would make it less brittle when cold and less tacky when warm .in the course of this work,he accidentally spilled a rubber-sulfur mixture on a hot stove and found that the resulting product had exactly the properties he was seeking.other chance discoveries include x-rays,radioactivity,and penicillin.so scientists and inventors always need to be alert to unexpected observations.perhaps no one was more aware of this than louis Pasteur,who wrote,"chance favors the prepared mind.