Its not always accurate because you dont know what they could have done to it before they try to sell it
Well a question to ask would be if the mass of the material has changed significantly as that would determine that the substance is radioactive or if there have been any high readings found by a Geiger meter in certain period of time
hope that helps
<em>Kinetic molecular Theory points:</em>
1. Gases molecules are always in random motion.
2. Gases molecule collide with each other and with the walls of container.
3. Gases molecules total volume is negligible as compare to container.
4. There is no attractive forces between the gases particles
5. K.E is directly proportional to absolute temperature.
<em>Why liquid are denser than gases according to K.M.T:</em>
1. As gases are in random motion, so they have weak forces/ no attractive forces (Acc. to KMT) due to this they are apart as compare to liquid which have stronger forces are closer to each other. So volume of gases will be greater. d= m/v
2. K. E of gases are greater than liquid due to this gases move randomly, apart from each another. Due to this their volume will be greater. d= m/v
3. Gases molecules total volume is negligible as compare to container which show that gases molecules have large spaces between them which causes lower in density.