Question

Liquid nitrogen was boiled in a styrofoam cup. Why was it critical the top of the cup not be covered? What happens as the liquid nitrogen boils away? What about the temperature gradient between the top of the liquid and the top of the cup versus the temperature gradient between the liquid and the wall of the cup?

What effect does frost buildup on the cup have on the shape of a weight versus time graph?

Answer 1

stryofoam cup is an polystyrene material as conducting/boiling process of nitrogen under lid closed condition makes an cup to freeze to lose its polymer property to rigid which results in collapse of stryofoam cup also partial pressure of nitrogen alsoplays an vial role during boiling as nitrogen boiling point is -195.8 centigrade so that top of the cup is not covered.

Nitrogen usually boils while comes in contact with warm object in this the layer of gas between nitrogen and object (cup) which leads to rollling drops during boiling atmost nitrogen never touches object during boiling, it any droplets gets holded results in frozening (coldspot).

Generally temperature gradient between liquid and wall of cup is most of time linear (gradual) at standard condition but in case of nitogen it is exponential in difference as warm receipt from wall of cup is gradual but inreturn is higher so gradient willnot be smooth in this case.

linear when comes to effect as it can be noted once all nitrogens gets boiled into atmosphere.