Explain what happens to substances during a chemical change.

The rock in a lead ore deposit contains 89 % pbs by mass. how many kilograms of the rock must be processed to obtain 1.5 kg of pb?

Which of the following describes a compound? (hint: carbon and oxygen bo a. a piece of pure carbon, containing only carbon atoms b. oxygen gas surrounding a solid piece of carbon c. a substance made of two oxygen atoms for each carbon atom carbon and oxygen atoms mixed without being bonded together

Elements in group 2 are all called alkaline earth metals. what is most similar about the alkaline earth metals?