Factual error: In the scene where the Professor Phillip first sees his creation (Flubber), he states that Flubber is 77 degrees Kelvin. Theoretically speaking, 77 degrees Kelvin is extremely cold, about -195 degrees Celsius (or -320 degrees Fahrenheit). The professor was handling Flubber with his bare hand at one point so he should've acquired one heck of a cold burn.
Factual error: When Robin Williams rides the car above the clouds, he is fine. At a level like that it can be hard to breathe as temperatures are often quite low when above the clouds, mainly below freezing point.
Chosen answer: It was rice and he just simply dumped them on the floor because he knew he wouldn't be needing it after the wedding to throw at the bride and groom because the Professor didn't show up.