Problem 1: serratia marcescens bacteria are used for the production of threonine. the maximum specific oxygen uptake rate of s. marcescens in batch culture is 4 mmol o2 g-1 h -1 . it is planned to operate the fermenter to achieve a maximum cell density of 50 g l-1 . at the fermentation temperature and pressure, the solubility of oxygen in the culture liquid is 8 × 10-3 kg m-3 . the concentration of oxygen in the culture liquid is 0.5 × 10-3 kg m-3 . at a particular stirrer speed, kla is 0.17 s -1 . under these conditions, will the rate of cell metabolism be limited by mass transfer?

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant. 

Convection is da answer my dood