Sound waves generated in a classroom must through an open doorway in order to propagate into the hallway.

diffract through an open doorway in order to propagate into the hallway.

Diffract

Explanation:

The diffraction of sound waves is the description of how sound waves bend, change direction, as they travel around the edges of obstacles. The diffraction occurs as a result of the bending of sound waves as they find the path of least resistance to the travel path. The amount and magnitude of the diffraction occurs in proportion to the opening in the obstacle pathway. The diffraction is a property of sound that helps it bend around the corners and obstacles.

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

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.