The phase change in which a substance changes from a soild toa gas or vapor without changing to a liquid first is

SUBLIMATION

is the phase change in which a substance changes from a solid to a gas or vapor without changing to a liquid first. When a gas or vapor changes directly into a solid without first changing to a liquid, the phase change is called deposition.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).

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.