Which of these is an indication that a chemical reaction has occurred? a) formation of a gas b) boiling of a substance c) melting of a substance d) freezing of a substance

Asample of silver (with work function ? = 4.52 ev) is exposed to an ultraviolet light source (? = 200 nm), which results in the ejection of photoelectrons. what changes will be observed if: silver is replaced with copper (? = 5.10 ev) more photoelectrons ejected no photoelectrons are emitted fewer photoelectrons ejected more energetic photoelectrons (on average) less energetic photoelectrons (on average)

As changes in energy levels of electrons increase, the frequencies of atomic line spectra they emit

Use the measurements in the table to determine which unidentified metal has the highest density. metal volume mass a 10.5 cm3 122 g b 14.2 cm3 132 g c 16.1 cm3 115 g d 12.7 cm3 126 g