Jeffery heard his teacher tell him what a great job he was doing. Was the wave that he heard a mechanical wave or an electromagnetic wave?

*tilts head* sounds more like a statement

if the temperature drops and becomes cool

then the atmosphere can be freezing as the water vapor in the air is at maximum (100%) and can be severely cold

also can be snowing lightly as the moisture in the air will start to solidify

and btw this is not chemistry but