What is a substance made of two or more elements that are chemically combined in a set ratio?

Which process does not require the presence of a physical substance in order to transfer heat? air in the atmosphere is heated by the ground. this warm air then rises, and cooler air falls. this is an example of what type of process? how is conduction different from radiation?

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.

12. calculate the hydroxide ion concentration of a solution with ph = 3.25. show all calculations leading to an answer