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

Compare and contrast physical changes with chemical changes.

Which statement correctly describes metallic bonds? a. they form when certain atoms lose electrons and other atoms gain electrons. b. they involve an attraction between anions and cations. they always involvpoth a metal and a nonmetal. d. they can only form between atoms of the same element. e. they form because electrons can move freely between atoms.

Using data from seismic waves, geologists have learned that earth’s interior is made up of several