For every literate, the first and foremost question run behind every task is WHY? This is the Question which creates a consciousness and awareness towards the job you do. The same time this is the only question which puts every listeners to put their heads down and frequently gets irritated. The usage and the time of usage of interrogative words are important over an experiment. There are enormous situations speakers never plan before conversing. Developing the abilities on usage of words develops cautiousness and one should have ostentatious attitude before they ensure they are precocious. Always all the "W" indexed words are informative and keep develops the bonding on performing the tasks. "When" interrogative word give sense to the listener to evaluate the speaker on his planning abilities. "What" usage  always takes the conversation more interesting and develop pleasing attitude on keen to know more. So always ensuring on performing new experiments