Why are 99.9% of metals (pure) way more expensive than 95% metals?

Which object forms when a supergiant runs out of fuel? a red giant a black hole a white dwarf a neutron star

In the cathode ray tube experiment, j. j. thomson passed an electric current through different gases inside a cathode ray tube in the presence of an electric field. in which two ways did this experiment change scientists’ understanding of the atom?

How would the number of moles (n) of o2 change if the atmospheric pressure doubled but all other variables stayed the same