How does E. Mulsion, celebrity food scientist, define a physical reaction and what examples does he give?

Incomplete question. However, I assumed you are referring to the comments made in the online animated video (Chemical and Physical changes)  by celebrity food scientist E. Mulson.

Explanation:

Recall in the video animation that E. Mulson defines physical reaction as occurring when "molecules in a substance stay the same, both before and after".

An example he gave was that of an orange getting juiced, the molecules remain the same before juicing, and after.

chemistry sucks a**

explanation:

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.