Wastewater at 600 gpm, containing 10 ppm (by weight) of benzene, is to be stripped with air in a packed column, operating at 25∘c and 2 atm, to produce water containing 0.005 ppm of benzene. the packing is 2-inch polypropylene flexirings. the vapor pressure of benzene at 25∘c is 95.2 torr. the solubility of benzene in water at 25∘c is 0.180 g∕100g. an expert∘in voc stripping with air suggests the use of 1,000 scfm of air (60 f, 1 atm). at these conditions, for benzene,

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it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.