How do full moon, crescent moon and new moon occur?

We have a “new Moon” when our Moon's orbit around Earth moves it between Earth and the Sun. ... A full Moon occurs when the Moon has moved in its orbit so that Earth is “between” the Moon and the Sun. Between the new and full Moon, the amount of Moon we see grows — or waxes from its right side toward its left side.

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.