What is the best definition of molecule?
A. A molecule is an atom that cannot be broken
down.
B. A molecule is a positively charged partide.
C. A molecule is the smallest part of a substance
that is still that substance

altitude, density, pressure

air gets less dense the higher the altitude and also the air pressure is less as altitude rises.

the number of protons in the nucleus of a given element. has slight luster and conducts electricity at high temperatures like metal.but like a nonmetal,boron is brittle and does not conduct electricity well at low temperatures. in graphite, carbon is a soft,brittle solid.it is reflective,ductile,or malleable.

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.