By using a periodic table, what element X would be based on its average atomic mass

How could a student test the effect of removing heat from a gas that is stored in a sealed container? what must occur in order for matter to change states?

Condensation happens when water vapor cools. true or false? ?

Substance a is a nonpolar liquid and has only dispersion forces among its constituent particles. substance b is also a nonpolar liquid and has about the same magnitude of dispersion forces among its constituent particles. when substance a and b are combined, they spontaneously mix.