Let me try: an example of a scientific question that can be investigated with an experiments is "at what temperature does iron melt"?Questions in physics ans chemistry are easily tested with experiments. an example of a scientific question that cannot be (I think) investigated with an experiments is "how does neuron activaton lead to us having the perception of free will"?Questions connected to human mind on a more general lever are not as easily tested with experiments: they need models rather than this.