After 32 days, 5 milligrams of an 80-milligram sample of a radioactive isotope remains unchanged. what is the half-life of this element?
(1) 8 days (3) 16 days
(2) 2 days (4) 4 days

Which is an example of the practical pursuit of alchemy? a. forming perfect substances. b. transforming base metals. c. developing metalworking techniques. d. linking spiritual characteristics with material substances.

What type of reaction fuels the processes seen here?

Which process transfers heat from inside earth to its surface? convection currents in mantle pulling away of tectonic plates drawing in of tectonic plates convection currents in crust